Spectral volume microprobe arrays

ABSTRACT

Methods and apparatus are provided for determining a characteristic of a sample of a material by the interaction of electromagnetic radiation with the sample. The apparatus includes a source of electromagnetic radiation, an optical assembly and a detector. The optical assembly sequentially illuminates a plurality of volume elements in the sample with an intensity distribution in the sample that drops off substantially monotonically from a first region in a first optical path and collects electromagnetic radiation emanating from each of the volume elements. The optical assembly collects the electromagnetic radiation emanating from each of the volume elements with a collected distribution that drops off substantially monotonically from a second region in a second optical path. The first and second regions at least partially overlap in each of the volume elements. The detector detects the collected electromagnetic radiation emanating from each of the sequentially illuminated volume elements to produce responses representative of the characteristic in each of the volume elements.

This application is a continuation-in-part of U.S. patent applicationSer. No. 08/510,041, filed Aug. 1, 1995, now U.S. Pat. No. 5,713,364,issued Feb. 3, 1998.

FIELD OF THE INVENTION

The present invention provides apparatus and methods to derive spatiallydifferentiated analytical information from an exposed surface byanalyzing the results of the interaction of electromagnetic radiationwith discrete volume elements of the sample. This is achieved byspatially limiting the probing beam to a small volume element andlimiting the accepted response detected from the same volume elementonly, scanning the sample at various depths along the axis of theoptical assembly formed by the beam to determine the interaction fromvolume elements at the different depths and collecting such data from aplurality of points in a plane generally perpendicular to the probingbeam.

BACKGROUND OF THE INVENTION

An important requirement exists for an instrument that will providerapid and automatic diagnostic information, for example of cancerous andotherwise diseased tissue. In particular, there is a need for aninstrument that would map the extent and stage of cancerous tissuewithout having to excise a large number of tissue samples for subsequentbiopsies. In the current art, the medical profession relies generally onvisual analysis and biopsies to determine specific pathologies andabnormalities. Various forms of biochemical imaging are used as well.Unique optical responses of various pathologies are being exploited inattempts to characterize biological tissue as well.

These prior art techniques, however, contain serious drawback asdocumented in copending application Ser. Nos. 08/510,041 filed Aug. 1,1995, now U.S. Pat. No. 5,713,364 issued Feb. 3, 1998, and 08/510,043filed Aug. 1, 1995, now abandoned, which are incorporated herein byreference.

For example, performing a tissue biopsy and analyzing the extractedtissue in the laboratory requires a great deal of time. In addition,tissue biopsies can only characterize the tissue based uponrepresentative samples taken from the tissue. This results in a largenumber of resections being routinely performed to gather a selection oftissue capable of accurately representing the sample. In addition,tissue biopsies are subject to sampling and interpretation errors.Magnetic resonance imaging is a successful tool, but is expensive andhas serious limitations in detecting pathologies that are very thin orin their early stages of development.

One technique used in the medical field for tissue analysis is inducedfluorescence. Laser induced fluorescence utilizes a laser tuned to aparticular wavelength to excite tissue and to cause the tissue tofluoresce at a set of secondary wavelengths that can then be analyzed toinfer characteristics of the tissue. Fluorescence can originate eitherfrom molecules normally found within the tissue, or from molecules thathave been introduced into the body to serve as marker molecules.

Although the mechanisms involved in the fluorescence response ofbiological tissue to UV excitation have not been clearly defined, thefluorescence signature of neoplasia appears to reflect both biochemicaland morphological changes. The observed changes in the spectra aresimilar for many cancers, which suggest similar mechanisms are at work.For example, useful auto-fluorescence spectral markers may reflectbiochemical changes in the mitochondria, e.g., in the relativeconcentration of nicotinamide adenine dinucleotide (NADH) and flavins.Mucosal thickening and changes in capillary profusion are structuraleffects that have been interpreted as causing some typical changes inthe spectroscopic record.

The major molecules in biological tissue which contribute tofluorescence emission under 337 nm near UV light excitation, have beenidentified as tryptophan (390 nm emission), chromophores in elastin (410nm) and collagen (300 nm), NADH (470 nm), flavins (520 nm) and melanin(540 nm). However, it should be noted that in tissue, there is some peakshifting and changes in the overall shape relative to the purecompounds. Accordingly, the sample can be illuminated with a UV beam ofsufficiently short wavelength and record responses from the aboveenumerated wavelengths of light in order to determine the presence ofeach of above identified contributions to tissues types.

It has been further shown that hemoglobin has an absorption peak between400 and 540 nm, while both oxyhemoglobin and hemoglobin have stronglight absorption above 600 nm. Blood distribution may also influence theobserved emission spectra of elastin, collagen, NAD, and NADH. Furthercompounds present in tissue which may absorb emitted light and changethe shape of the emitted spectra include myoglobin, porphyrins, anddinucleotide co-enzymes.

A general belief is that neoplasia has high levels of NADH because itsmetabolic pathway is primarily anaerobic. The inability of cells toelevate their NAD+:NADH ratio at confluence is a characteristic oftransformed cells related to their defective growth control. The ratioof NADH+:NADH is an indicator of the metabolic capability of the cell,for example, its capacity for glycolysis versus gluconeogenesis. Surfacefluorescence has been used to measure the relative level of NADH in bothin vitro and in vivo tissues. Emission spectra obtained from individualmyocyte produces residual green fluorescence, probably originating frommitochondrial oxidized flavin proteins, and blue fluorescence isconsistent with NADH of a mitochondrial origin.

Collagen, NADH, and flavin adenine dinucleotide are thought to be themajor fluorophores in colonic tissue and were used to spectrallydecompose the fluorescence spectra. Residuals between the fits and thedata resemble the absorption spectra of a mix of oxy-anddeoxy-hemoglobin; thus the residuals can be attributed to the presenceof blood.

Alfano, U.S. Pat. No. 4,930,516, teaches the use of luminescence todistinguish cancerous from normal tissue when the shape of the visibleluminescence spectra from the normal and cancerous tissue aresubstantially different, and in particular when the cancerous tissueexhibits a shift to the blue with different intensity peaks. Forexample, Alfano discloses that a distinction between a known healthytissue and a suspect tissue can be made by comparing the spectra of thesuspect tissue with the healthy tissue. According to Alfano, the spectraof the tissue can be generated by exciting the tissue with substantiallymonochromatic radiation and comparing the fluorescence induced at leastat two wavelengths.

Alfano, in U.S. Pat. No. 5,042,494, teaches a technique fordistinguishing cancer from normal tissue by identifying how the shape ofthe visible luminescence spectra from the normal and cancerous tissueare substantially different.

Alfano further teaches, in U.S. Pat. No. 5,131,398, the use ofluminescence to distinguish cancer from normal or benign tissue byemploying (a) monochromatic or substantially monochromatic excitationwavelengths below about 315 nm, and, in particular, between about 260and 315 nm, and, specifically, at 300 nm, and (b) comparing theresulting luminescence at two wavelengths about 340 and 440 nm.

Alfano, however, fails to teach a method capable of distinguishingbetween normal, malignant, benign, tumorous, dysplastic, hyperplastic,inflamed, or infected tissue. Failure to define these subtledistinctions in diagnosis makes appropriate treatment choices nearlyimpossible. While the simple ratio, difference and comparison analysisof Alfano and others have proven to be useful tools in cancer researchand provocative indicators of tissue status, these have not, to date,enabled a method nor provided means which are sufficiently accurate androbust to be clinically acceptable for cancer diagnosis.

It is quite evident from the above that the actual spectra obtained frombiological tissues are extremely complex and thus difficult to resolveby standard peak matching programs, spectral deconvolution orcomparative spectral analysis. Furthermore, spectral shifting furthercomplicates such attempts at spectral analysis. Last, laser fluorescenceand other optical responses from tissues typically fail to achieve depthresolution because either the optical or the electronic instrumentationcommonly used for these techniques entail integrating the signal emittedby the excited tissue over the entire illuminated tissue volume.

Rosenthal, U.S. Pat. No. 4,017,192, describes a technique for automaticdetection of abnormalities, including cancer, in multi-cellular bulkbiomedical specimens, which overcome the problems associated withcomplex spectral responses of biological tissues. Rosenthal teaches thedetermination of optical responses (transmission or reflection) datafrom biological tissue over a large number of wavelengths for numeroussamples and then the correlation of these optical responses toconventional, clinical results to select test wavelengths and a seriesof constants to form a correlation equation. The correlation equation isthen used in conjunction with optical responses at the selectedwavelengths taken on an uncharacterized tissue to predict the status ofthis tissue. However, to obtain good and solid correlations, Rosenthalexcises the tissues and obtains in essence a homogeneous sample in whichthe optical responses do not include the optical signatures ofunderlying tissues. Rosenthal's methods, therefore, cannot be used invivo applications as contemplated in the present invention.

In studies carried out at the Wellman Laboratories of Photomedicine,using a single fiber depth integrating probe, Schomacker has shown thatthe auto-fluorescence of the signature of human colon polyps in vivo isan indicator of normality, benign hyperplasia, pre-cancerous, andmalignant neoplasia. See Schomacker et al., Lasers Surgery and Medicine,12, 63-78 (1992), and Gastroenterology 102, 1155-1160 (1992). Schomackerfurther teaches using multi-variant linear regression analysis of thedata to distinguish neoplastic from non-neoplastic polyps. However,using Schomacker's techniques, the observation of mucosal abnormalitieswas hindered by the signal from the submucosa, since 87% of thefluorescence observed in normal colonic tissue can be attributed tosubmucosal collagen.

Accordingly, there is a need for a more effective and accurate device tocharacterize specimen, and particularly in vivo specimen which willobtain responses from well defined volume elements within said specimen,and present data automatically from a relatively large area comprising aplurality of such volume elements. Furthermore, there is a need formethods to automatically interpret such data in terms of simplediagnostic information on said volume elements.

In the aforementioned applications, Ser. Nos. 08/510,041 and 08/510,043,Modell, DeBaryshe and Hed taught the general principles of obtainingvaluable analytical data from a volume element in a target sample byusing spatial filters with dimensions that are generally larger than thediffraction limits for the wavelengths of the probing radiation. Suchspatial filtration is obtained by an optical device including anillumination and a detection system both containing field stops and thefield stops being conjugated to each other via the volume element to beanalyzed, providing in essence a non imaging volume microprobe.

While the family of devices described in the aforementioned applicationare very useful in the analysis of a plurality of points within a targetsample, there is a need to easily and automatically obtain such data ona full array of points so as to convert these data to an artificialimage of the analytical findings over a large area of the sample. Thisis particularly important when heterogeneous samples, such as biologicalsamples are examined with the non imaging volume microprobe. Forinstance, when examining tissues to determine the presence or absence ofoncological pathologies, or other pathologies, visual techniques arefollowed, in some cases, by the resection of biopsy specimen. Suchtechniques are naturally limited in that the physician eye can onlyassess the visual appearance of potential pathologies, and the number ofbiopsies taken is by necessity limited. The appearance of pathologicaltissues does not provide information on the depth of the pathologies,and cannot provide positive diagnosis of the pathology. Furthermore,since biopsies are carried out ex vivo, a time lag between the taking ofthe biopsy and obtaining its results cannot be avoided. It would be veryuseful for physicians to have a device capable of performing suchdiagnostic tasks in vivo and to obtain differential diagnostics (betweenhealthy and pathological tissues) while performing the examination. Thisis particularly important when performing exploratory surgicalprocedures, but can be very useful when examining more accessibletissues as well.

A number of devices have been described in the prior art relatingparticularly to confocal microscopy where illumination and detectionarrays are provided. For instance, a confocal scanning microscope inwhich mechanical scanning of the illuminating and the transmitted (orthe reflected) beams is avoided is described in U.S. Pat. No. 5,065,008.A light shutter array is used to provide synchronous detection of ascanned light beam without the need to move a photodetector to followthe scanning beam, and each of the shutters is serving, in essence, as afield stop in the confocal microscope. In other embodiments, twooverlapping arrays of liquid crystals are used as optical shutter arraysto attempt reduction in the size of the field stops. As is well known inthe art of confocal microscopy, in order to obtain the desiredresolution afforded by this technique, the dimensions of the field stopsneed to be small relative to the diffraction limit of the optical beamused in the system. Other embodiments also provide for two sets of fieldstops, conjugated within the sample, one set for the illuminating beamand one set for the transmitted or reflected beam. While this patentteaches the use of electronic scanning of the illumination and responsebeams, the illumination intensity and response signal strength aredrastically limited due to the use of dual liquid crystal opticalshutters required to achieve the pin-hole effect of a scanning confocalmicroscope.

Another confocal imaging device is taught in U.S. Pat. No. 5,028,802,where a microlaser array provides a flying spot light source in aconfocal configuration. Similarly U.S. Pat. No. 5,239,178 provides foran illuminating grid for essentially the same purpose, except that lightemitting diodes are used for the grid's light sources. These approaches,however, are limited to monochromatic illumination and are usable onlywith relatively long wavelengths at which solid state laser diodes andthus microlaser arrays or light emitting diode arrays are available.

None of these devices provide for an array of non-imaging volumemicroprobes. Accordingly, there is a need for a device comprising anarray of non-imaging volume microprobes in which a plurality of volumeelements in a sample can rapidly be scanned in order to obtaindiagnostic or analytical information over a relatively large area of thesample without integrating the data from all the sampled volumeelements.

SUMMARY OF THE INVENTION

In the present invention, the principles taught in the aforementionedapplication are applied to automatically obtain optical responses from athree dimensional array of such volume elements by providing a pluralityof non imaging volume microprobes in parallel which automaticallypresents mapping of the diagnostic information sought, in a planegenerally parallel to the surface of the specimen (the xy plane) and inthe z direction which is generally perpendicular to the xy plane.

The optical responses from an array of volume elements are furtheranalyzed to provide visually (namely on a monitor) information which isnot readily available by direct examination of the specimen. This isachieved by, in essence, providing an artificial three dimensionalbiochemical map composed from the optical responses, or more accurately,derivatives of such responses, of each individual volume elementexamined in an array, and by further converting these biochemical datato an artificial pathological image delineating the nature, extent anddepth of pathologies observed. This is achieved by creating anartificial pathological scale, for each pathology of interest, bytraining the instrument to recognize specific pathologies. Specifically,a training set of specimens on which optical responses with a nonimaging volume microprobe were collected, is subjected to a rigorouslaboratory determination of the pathological state of each of itsspecimens and a value is assigned to each specimen on the artificialpathological scale. A set of linear equations relating to the responses(or functions of the responses) for each specimen to the pathologicalstates, is constructed and optimized solutions for the correlationcoefficients sought. These correlation coefficients are then used totransform responses obtained on unknown specimen to obtain thepathological state of these unknown specimen.

The objectives of the instant invention are achieved by providing anarray of optical assemblies each consisting of two conjugated, orpartially conjugated, optical assemblies. In each such assembly, thefirst optical assembly is designed to image selectively a transmittedbeam from a light source, or another source of radiation, within aplurality of selected volume elements of a sample in a sequentialmanner. The second optical assembly is designed to collect light, orradiation emanating from the volume elements, in the same sequentialmanner, and transmit the collected light or radiation to a detector forfurther analysis of the interaction of the first transmitted beam withthe volume elements. The first optical assembly includes a first fieldstop to achieve selective illumination of a selected volume element, andthe second optical assembly includes a second field stop to restrictacceptance of said emanating radiation or light into the collectionoptics, essentially only from the selected volume element. Furthermore,a controller is provided to adjust the depth of the selected volumeelements relative to the surface of the sample by controlling therespective focal points of the two optical assemblies while keeping themconjugated and having the volume element as a common conjugation pointfor both optical assemblies.

Sequential illumination of the various volume elements in an array isdesired to assure that only responses from a given volume element arecollected by the optical assembly associated with the volume element atany given time.

The sequential illumination of a plurality of volume elements can becarried out with a variety of devices. In some embodiments of theinvention, an array of optical shutters is interposed between the lightsource and the sample, each shutter serving as either a field stop or anaperture stop for a specific optical assembly. In some embodiments, asingle array of optical shutters is provided, while in other embodimentstwo arrays of optical shutters are provided. In yet another embodimentof the invention, an array of micromirrors is used to control thesequential illumination and response collection of the various volumeelements in the sample. In yet another embodiment of the invention, anarrayed bundle of optical fibers is used to sequentially illuminate anarray of volume elements in the sample and to collect sequentiallyresponses from the volume elements. Appropriate movement of the opticsso as to probe various depths of the sample is provided.

The optical responses from the selected volume elements bear importantinformation about the volume elements, such as chemistry, morphology,and in general the physiological nature of the volume elements. When thesample is spectrally simple, these optical responses are analyzed byclassical spectral techniques of peak matching, deconvolution orintensity determination at selected wavelengths. One such system couldbe the determination of the degree of homogeneity of a mixture or asolution of a plurality of compounds. However, when the samples arecomplex biological specimens, as mentioned above, the spectralcomplexity is often too great to obtain meaningful diagnosis. When suchbiological specimens are analyzed for subtle characteristics, wesurprisingly found that the application of correlation transforms tospatially filtered optical responses obtained from an array of discretevolume elements, or the use of such transforms in conjunction with dataobtained through non imaging microscopy, yields diagnosticallymeaningful results.

Specifically, we first select a training sample of a specific targetpathology. Such a sample will preferably have at least 10 specimens.Optical responses are first collected from well defined volume elementsin the specimens and recorded. These optical responses can be taken withan array microprobe or with a single volume microprobe device asdescribed in the aforementioned co-pending application. The same volumeelements that have been sampled with the non imaging volume microprobeare excised and biopsies (namely cytological analysis of the excisedvolume elements) is carried out in a classical pathological laboratoryand the specimens are scored on an arbitrary scale which relates to theextent of the pathology, C (for instance a specific cancer) beingcharacterized. These scores, C_(j), where C_(j) is the score valueassigned to the specimen j within the training set, should be asaccurate as possible, and thus an average of a number of pathologists'scores (determined on the same volume elements, j), can be used. We nowcreate a set of equations Σa_(ic) F(I_(ij))=C_(j), where i designates arelatively narrow spectral window (usually between 5 and 50 nm) and thusF(I_(ij)) is a specific function of the response intensity or othercharacteristics of the spectral response in the window i for volumeelement j. The function F is sometimes the response intensity itself, inthat window, namely, F(I_(ij))=I_(ij), orF(I_(ij))=(dI_(ij))/dλ)/I_(ij), where λ is the median wavelength in thewindow i, or other functions. The factors a_(ic), the correlationtransform's coefficients for the pathology C, are now found from the setof equations created above, by means well known in the prior art, suchas multivariate linear regression analysis or univariant linearregression analysis. In such analysis, the number of wavelength windowsi required to obtain faithful correlations between the optical responsesand the pathological derivations of the values C_(j), is minimized andthe set of correlation coefficients a_(ic) for the pathology, C arefound. When we now record the responses (I_(ik)) (which is a vector inthe space of i optical windows, now minimized to a limited number ofdiscrete elements) on a sample outside the training set and apply thetransform operator (a_(ic)) on the vector F(I_(ik)), namely obtain thesum Σa_(ic) F(I_(ik))=C_(k), we automatically obtain the score for thetarget pathology C for the volume element sampled.

It should be understood that other statistical tools, such as principalcomponent regression analysis of the optical responses, could be used aswell. One can also consider using in the correlation transforms, in lieuof functions of the optical responses at specific wavelengths, theFourier transform of the total spectral responses. Furthermore, whiletaking the spectral responses from specific volume elements, theseresponses can be treated optically through either a spatial Fouriertransform generator (such as a Sagnac interferometer) or a temporalFourier transform generator (such as a Michelson interferometer), andthen the data obtained can be used to create the desired correlationmatrices to train the system for further data acquisition and imagegeneration of the distribution of possible pathologies.

Instruments embodying the invention are deemed useful for obtainingartificial images of some characteristics of turbid materials, such asbiological tissue, plastics, coatings, and chemical reaction processes,and may offer particular benefits in analysis of biological tissue, bothin vitro and in vivo. To provide internal analysis, the invention isadapted to work with existing endoscopes, laparoscopes, or arthroscopes.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic and generalized block diagram of the majorelements of the present invention.

FIG. 2 is a block diagram of an embodiment of the invention with anarray of light valves, in which each light valve acts as an addressablefield stop for the illumination and detection beams.

FIG. 3 illustrates an embodiment where an array of lenslets of the sameperiodicity as the array of light valves acts as an array of objectivelens for both the illumination and detection beams.

FIG. 4 and FIG. 4A illustrate embodiments of the invention in whichseparate illumination and detection light valves arrays create arrays ofaperture stops, each in conjunction with lens arrays serving asobjectives for the illumination and detection optics. In FIG. 4A, thedetection lens array is replaced with a single lens.

FIG. 5 illustrates an embodiment of the invention in which an array of(deformable) flat micromirrors is used as field stops and the sequentialselection of micromirrors serves to sequentially illuminate volumeelements in a sample.

FIGS. 6 and 6A show embodiments of the invention in which an array of(deformable) off axis parabolic mirrors serve as selecting objectives tosequentially apply excitation beams to various volume elements andcollect the responses from the volume elements.

FIG. 7 shows an embodiment of the invention in which the light shutterarray is replaced with a fiber switching device to sequentiallyilluminate (and obtain responses from) an array of volume elements in atarget sample.

FIG. 8 illustrates an embodiment having two optical assemblies, eachcoupled to its own (excitation and detection) fiber bundles in whichsequential illumination of fibers (and detection) is practiced to obtaindata from an array of volume elements.

FIGS. 9 and 10 illustrate embodiments of the invention in which lightshutter arrays are coupled to optical fiber bundles.

FIG. 11 is a schematic representation of one of the embodiments of theinvention, including a block diagram of the control and data processingelements of the system.

FIG. 12 is a block diagram that illustrates methods of using volumeprobe arrays of the invention, particularly in the diagnostic of variouspathologies.

FIGS. 13a and 13b are bottom and top views, respectively, of a partialsegment of a PVDF based optical shutter array.

FIG. 14 shows another embodiment of a PVDF based optical shutter array.

FIG. 15 is a top view of a micromachined optical shutter array.

FIG. 16 shows another embodiment of a micromachined optical shutterarray.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 we show a generalized schematic volume probe array, 10, whosefunction is to collect data from a plurality of points in a targetsample. The system generally includes an appropriate light source 11,whose light output is conditioned and may be multiplexed in block 12 tocreate a plurality of light sources to be relayed to an array 13 oflight valves. These light valves can act as illuminating field stops oraperture field stops, and only one valve is open at a given time, thusproviding for sequential illumination of volume elements in sample 19.The light emanating from each light valve is then directed to a targetedvolume element in the sample 19 with an appropriate illuminationobjective 14. In some embodiments, a single objective lens is used,while in other embodiments, we incorporate an array of objectivemicrolens having the same periodicity as that of the light valve array.

Responses from each targeted volume element in the form of lightemanating from the volume elements, is collected through a collectionoptics objective 15 (which in some embodiments can be the same as theillumination objective and an array of microlens), and through an array16 of light valves (which can also be the same array as the one used forillumination). The responses are then directed to one or more detectors17 to determine their optical and spectral characteristics.

It should be emphasized that both the illumination optics and thecollection optics each contain a field stop having dimensions that arerelatively large in relation to the average wavelength of theilluminating radiation, and furthermore, these field stops areconjugated to each other through the volume element examined. As aresult, a well defined volume element is illuminated at any time, andthe optical response from the element collected through the field stopof the collection optics is essentially limited to responses emanatingfrom the volume element.

A controller 18 is provided to control the sequencing of the volumeelements scanned (in the x,y plane, the plane of the sample) and tocontrol the depth of the volume elements examined (in the z direction.)

In FIG. 2, a simple example of an array volume microprobe system 20 isshown. The system includes a light source 21. Light from the lightsource is condensed with a lens 22 onto an array of light shutters 24,through a beam splitter 25. In this embodiment, each element 28 in thelight shutter array serves as a field stop which is being imaged throughan objective lens 26 on a sample 27. The dimensions and shape of theshutters determine the morphology of volume elements sampled in a mannerdiscussed in detail in copending applications, Ser. Nos. 08/510,041 and08/510,043. In essence, the mean dimension, d, of each shutter isselected to be larger than the wavelength divided by the numericalaperture, NA, of the objective or d>>λ/NA. Thus the image of the fieldstop in the plane of the sample is larger than the diffraction limitedresolution for the wavelength. As a result, a very large proportion ofthe light that traverses a given field stop and is imaged in the sampleis within a well-defined volume element of the sample. Similarly, whilethe total response to the illumination is distributed over a very largespatial angle (essentially 4π steradians), only responses that areemanating from within the same volume element are imaged back onto thefield stop and reach detector 29, by being reflected on the beamsplitter 25 onto a collector lens 23 which concentrates the responseonto the detector 29. This results from the fact that the respectivefield stops of the illumination and detection systems are conjugated toeach other via the target volume element. In the embodiment shown inFIG. 2, both field stops are embodied within the same aperture (anoptical shutter or a light valve 28 within the optical shutter array).

In some embodiments, the beam splitter 25 can be a dichroic mirror,particularly when the light source is a short wavelength (UV) excitinglight source and the responses are fluorescence responses. In otherembodiments, the beam splitter 25 can be a half silvered mirror whichseparates the optical path of responses from the sample from the opticalpath of the exciting beam, for instance, when the exciting beam isprovided with a broad spectrum light source, and the responses involveback scattering and reflections from the sample (and thus mostly theextent of absorption of the exciting beam in the targeted volume elementis examined).

The array of light valves, or optical shutters, can be implemented in anumber of different ways. One can use liquid crystal sandwiched betweentwo electrode arrays (deposited, as is in the prior art on transparentglass or plastic sheets in the form of transparent electrodes made ofIndium Tin Oxide (ITO) or Tin Oxide (TO), usually doped with fluorine toprovide good areal conductivity). One can also use films of PDLC(polymer dispersed liquid crystals) that might be easier to handle andhave lower production costs. Another embodiment contemplated, when therequired scanning is particularly fast, is an array of ferroelectricelements, each acting as a light valve. Yet another embodiment of thelight valves can involve an array of PVDF (Polyvinyl-difluoride)bimorphs, each coated to be reflective (or opaque on both sides) on theside facing the light source and designed to bend out of the light pathso as to create a light valve. The typical dimensions of the light valverange from a low of about 20 microns to as much as 1000 microns. Thesize is determined primarily by the application, the nature of thesample analyzed and the particular design of the specific array volumemicroprobe utilized. When using the general design of FIG. 2, with asingle large objective lens serving as a common objective to all thefield stops in the array, the space between adjacent light valves isusually kept as small as possible, so as to provide as closely spaced aspossible scanned volume elements. It should be understood however thatin some embodiments, the spacing is kept relatively large (as large asthe field stop itself) when an image of the pathology consisting of wellspaced discrete points is more appropriate.

In operation, the controller 18 keeps one of the light valves open andadjusts the position of the device so as to image the field stop at thedesired volume element in the sample 27. Once the general position ofthe device relative to the sample has been optimized, the controllercauses scanning of the surface of the specimen in the xy (the plane ofthe specimen) direction by sequentially closing an open light valve andopening an adjacent light valve. The time interval of each light valvein the open position is a strong function of the intensity of the lightsource and the efficiency of collection of the responses from eachvolume element. In some embodiments, this time interval can be shorterthan a millisecond, while in other embodiments tens to hundredsmilliseconds are required.

The controller 18 also controls the position of the volume elementswithin the sample in the z direction, generally an axis perpendicular tothe plane of the samples. This can be achieved in a number of ways. Forinstance, the whole optical assembly can be moved back and forth in thez direction. In some embodiments, this translational movement of theimage plane of the field stops in the sample can be achieved by movingthe objective alone, or the array of light valves, or both of theseelements simultaneously. The specific design depends on the particularembodiment of the device.

It should be appreciated that since the intensity of illumination ishighest within the volume element probed by the excitation beam(relative to zones surrounding the volume element), and that theresponse detected by the sensor 29 is primarily from the same volumeelement (and contains very little illumination emanating from zonessurrounding the volume element), that changing the position of thevolume element within the sample in the z direction will provideresponses from various depths of the sample. This, in essence allows foranalysis, in vivo of tissues at various depths, as long as the overallabsorption of the illuminating beam by the tissue and the responses tothe beam are not excessive.

In FIG. 3, a slightly different embodiment of an array volume microprobe30 of the present invention is shown. The system includes a light source31 with appropriate optics (not shown) to project a common field stop 41through a condenser lens 32 onto an addressable shutter array 34. Eachelement in the addressable shutter array can be considered an aperturestop which serves to further limit the spatial distribution of the lightimpinging on a sample 37. In lieu of using a large singular objective(as used in the embodiment described in FIG. 2) to image the field stopon each volume element in the sample 37, a lens array 36 is interposedbetween the shutter array and the sample. The lens array 36 consists ofa plurality of microlens 42. The periodicity of the lens array isexactly the same as that of the shutter array, and each lens 42 withinthe lens array 36 corresponds to a light valve 38 within the lightshutter array 34. In most embodiments, the light impinging on theshutter array would be collimated, and the shutter array would be fixedin position relative to the lens array. The volume element probed wouldbe at the focal point of the objective lens within the microlens array,and movement of the combination of the shutter and lens array in the zdirection, can be used to probe different layers within the sample, asexplained above when describing the array volume microprobe of FIG. 2.One can, however, conceive of other arrangements where the lens arrayand the shutter array are capable of moving independently, and probingthe sample in the z direction is achieved by translation in the zdirection of the lens array alone.

Light responses to the exciting radiation from the light source 31 fromeach of the sampled volume elements are collected through the sameobjective elements through which illumination is effected. The lightresponses are separated from the illuminating beam by the beam splitter35. These responses are then imaged via a collecting lens 33 onto acollection field stop 43 that restricts the responses received by asensor 39 to be essentially only from the probed volume element. Inoperation, the controller 18 opens a given shutter and allows theillumination of a single volume element. Furthermore, the same lightshutter allows optical responses to the excitation to be recorded by thedetector 39. This is followed by closing the light valve and openinganother light valve, so that sequentially discrete volume elementswithin the sample are scanned to obtain optical responses thereof. Onecan scan all the desired volume elements in the array in a given x,yplane and then rescan the array at a different depth (in the z axis), soas to obtain three dimensional information on the target sample. One canalso choose to operate the array volume microprobe in such a way thatfor each pixel, the respective light valve 38 is kept open, while thecontroller causes the shutter array together with the lens array to movein the z direction, thus probing at the same x,y location volumeelements at various depths of the specimen.

In yet another embodiment of the array volume microprobe, theilluminating and detecting optics are each provided with their own arrayof optical shutters. In FIG. 4, such an embodiment is shownschematically. Specifically, the array volume microprobe 50 includes alight source 51, a first field stop 52, a collimating lens 53, a firstshutter array 54, a first objective lens array 55, beam splitting means56, a second objective lens array 58, a second shutter array 59, asecond collimating lens 60, a second field stop 61 and a detector 62.Not shown in FIG. 4 are appropriate means to image the light source 51and detector 62 onto their respective field stops 52 and 61. Inoperation, the light source 51 is imaged onto the field stop 52, havingdimensions that are greater than the diffraction resolution limits ofthe exciting radiation. The light emanating from the field stop 52 iscollimated into an essentially parallel beam that impinges on the backside of the shutter array 54. At any given time, only one of the lightvalves in the light shutter array is opened and its corresponding lightvalve in the detector shutter array is open. The sequential illuminationof an array of volume elements within the sample, in a manner similar tothat described above, coupled with the synchronous opening of theappropriate light valve in the detector array, assures that at any giventime, only responses from the probed volume element are detected.Similarly, scanning in the x,y direction is provided by controller 18sequencing the opening and closing of the light valves in the twoshutter arrays in synchronism. It should be understood that in thisembodiment, the two field stops 52 and 61 are conjugated to each othervia each of the volume elements 63 in the sample 57.

In FIG. 4A, an arrangement essentially identical to that described inFIG. 4 is shown, except that the array of microlens 58 is replaced witha single large lens 58'. Like elements in FIGS. 4 and 4A have the samereference numbers.

Yet another embodiment of the invention is illustrated in FIG. 5, whichshows an array volume microprobe 70. The system includes a light source71 and a detector 72 having their optical axes orthogonal to each otherand separated by a first beam splitter 73. The light emanating from thesource is condensed onto an array of field stops 74 with a condenserlens 75 and a second beam splitter 76. The array of field stops 74consists of an array of micromirrors 77 that can be tilted in and out ofa plane generally parallel to the plane of the array. Light reflectedfrom any one of these mirrors, while in the untilted position, isreflected back through the second beam splitter 76 and is imaged onto asample 79 with an objective lens 77. As shown in FIG. 5, only onemicromirror 78 at any given time is oriented to reflect light onto thesample. All other micromirrors in the array are tilted so that lightimpinging on them is reflected away from the sample. In FIG. 5, rays 1and 4 are limiting rays for the total field, and rays 2 and 3 arelimiting rays for a single micromirror. In operation, the micromirrors77 are sequentially brought to the untilted position by the controller18, and as a result of this sequential untilting of micromirrors, asequence of responses from volume elements in the sample 79 is recordedin the detector 72. An artificial image from the responses can then berecorded and displayed. As in prior embodiments, probing of the samplewith the volume microprobe array in the z direction (depth) can beachieved by either moving the objective lens 77 or the array 74 in the zdirection.

The control of the tilting mirror is performed by controller 18, and thetilting mechanism can be implemented in a number of ways well known inthe prior art. For instance, the mirrors can be micromachined insilicon, leaving a cantilever in the middle of the back of the mirrors.Two opposing electrodes cause the mirror to tilt about the cantileverdue to charging one or the other electrode with a charge opposing thecharge on the mirror itself. Another method of obtaining tilting mirrorsis well known in the art of deformable mirrors, whereby each micromirroris mounted on a bipolar piezoelectric element.

Yet another embodiment of the invention, a variation of the embodimentshown in FIG. 5, is illustrated in FIG. 6. An array volume microprobe 80includes a light source 81 from which light is conditioned to passthrough a first field stop (not shown) and through a lens 82. The lightis collimated onto an array of micromirrors 83. The micromirrors aretiltable as described above. However, each of the micromirrors is shapedto be an off axis segment of a paraboloid of revolution having its focalpoint tracing an arc of radius which is somewhat larger than thedistance of the array from the sample. The geometry is such that whenthe mirrors are untilted (parallel to the plane of the array), the axisof the paraboloid of revolution (of which the specific mirror is an offaxis segment) is perpendicular to the plane of the array. Thus a linebetween the focal point (of the paraboloid of revolution) and themicromirror is at a predetermined angle to the normal to the array. Themicromirrors can be tilted through that angle so as to bring the focalpoint of the paraboloid onto the sample.

In one embodiment of the invention, the micromirrors are arranged inalternating right rows 89 and left rows 88 of off-axis segments of aparaboloid. The right mirrors can be termed the exciting mirrors and theleft mirrors the detecting mirrors. The focal points of each segment ofright rows 89, upon tilting at the above mentioned angle, resides withinthe sample at the volume element 85, and its respective paraboloid axisof revolution is parallel to the optics axis of the exciting beam, whilethe tilting in the opposing direction (at the same angle) of eachmicromirror in an adjacent left row causes the focal point of eachmicromirror to move to the same volume element (85) in the sample 84,and its respective paraboloid axis of revolution is parallel with theoptics axis of the detector. Thus, all mirrors in right rows 89 are usedto excite volume element 85 in the sample 84 and all left rows 88 areused to collect responses from volume element 85. In operation, only onepair of mirrors is tilted at any given time and the axes of all othermirrors point down toward the sample. As a result, an exciting beam fromthe light source 81 is imaged onto the volume element 85, or moreaccurately, the first field stop is so imaged, while light impinging onall other mirrors is scattered away from the sample in all directions.Similarly, only responses emanating from the volume element 85 areimaged back onto the second field stop in front of the detector. As aresult, a very high degree of discrimination is obtained, since theintensity of the exciting beam decreases very rapidly outside of volumeelement 85, and responses from outside volume element 85 are essentiallyblocked by the second field stop in front of the detector 87. Thecontroller 18 controls the sequence of tilting each pair of mirrors toobtain an array of responses from different volume elements in thesample. The depth of the volume element in the sample is also controlledby the controller 18 by moving the total array 83 along the z axistoward or away from sample 84.

A slightly modified embodiment of the volume probe array shown in FIG. 6is presented in FIG. 6A. This embodiment allows for using each off axisparabolic micromirror both as an excitation and detection mirror. Thesystem is equivalent to that shown in FIG. 6 and described above, exceptthat the micromirrors of array 83' of the volume probe array 80' arerotated by 90° to the right or the left. Thus, in the unrotatedposition, the axis of revolution (and thus the optical axis) of eachmirror is at 90° to the optical axis of the exciting and detectingoptics. However, when a mirror 89' is rotated by 90° to the right, itsaxis of revolution becomes parallel to the axis of the excitation, andthe focal point of the off-axis parabolic micromirror is in volumeelement 85'. If an adjacent mirror 88' is simultaneously rotated 90° tothe left, then its axis of revolution becomes parallel to the detectionoptics, and its focal point is in volume element 85'. The volume element85' is determined by the overlap of the images of the two field stops,as explained in detail in copending application Ser. Nos. 08/510,041 and08/510,043. In this embodiment, as well as the one shown in FIG. 6,sheared conjugation of the excitation and detection optics field stopsis used to provide for spatial discrimination of the excitation beam tothe target volume element as well as the spatial discrimination of thedetected responses to be essentially from each volume element. Inoperation, the controller 18 causes two adjacent micromirrors (89' and88') to be rotated simultaneously as described above and thus providesexcitation of essentially only the desired volume element 85' andresponses which emanate essentially from the volume element 85'.

An advantage of the embodiment shown in FIG. 6A is that a higherresolution of volume elements is feasible for the same density ofmicromirrors, since each mirror can be used to either excite a volumeelement or to collect responses from an adjacent volume element. Thisdiffers from the embodiment shown in FIG. 6, where all left mirrors canbe used only to collect responses and all right mirrors can be used onlyto excite volume elements. In the embodiment of FIG. 6, the tilting ofthe off-axis paraboloids of each segment is in a plane perpendicular tothe plane of the array, while in the embodiment of FIG. 6A, the plane ofrotation is parallel to the plane of the array.

In FIG. 7, yet another embodiment of the invention is shown. An arraymicroprobe 90 includes an illumination optical assembly with a lightsource 91 and a first collimating lens 92, and a response collectionoptical assembly having a detector 93 and a second collimating lens 94.The respective optical axes of the light source assembly and thedetector assembly are at 90° to each other. A beam splitter 95 ispositioned at the intersection of the exciting and detected beam so asto separate the detected signal from the excitation signal. A lens 96 isused to focus the exciting beam into an optical fiber 102 which isinterfaced with a fiber switching element 97. The fiber switchingelement 97 is terminated on the opposing side with a plurality of fibers98, and the switching element is capable of connecting optically andsequentially (under the control of the controller 18) the proximal fiber102 to any of the fibers 98 in the distal bundle. The ends of theindividual fibers in the bundle are then arranged in an array 99 (thisarray may be either a linear array or a two dimensional array). Anobjective lens 100 then images the respective ends of the fibers in thefiber bundle onto the specimen. Each individual fiber end (within thefiber holder) defines a field stop which is imaged onto the sample. Thisfield stop serves as a field stop to both the exciting beam and thedetected responses from the sample. As is described in more detail incopending application Ser. Nos. 08/510,041 and 08/510,043, such anarrangement involves the conjugation of both the exciting and detectedoptics via the volume elements in which the field stop is imaged, andthus provides for spatial discrimination of both the excitation beam andthe responses to be essentially from each volume element associated witheach fiber in the array.

In operation, the fiber switching element 97 directs the exciting beamsequentially through all the fibers in the bundle 98. As a result, aplurality of volume elements in the sample 101 (having a distributioncorresponding to the array of fibers in the bundle 98) are excitedsequentially. Responses are collected through the same field stop (thenatural aperture of each fiber end) and are separated from the excitingbeam by the beam splitter 95 to be detected in detector 93. In thismanner, one obtains responses from an array of volume elements that canthen be displayed as an artificial image of the sample. This embodimenthas the advantage that a higher intensity of excitation is feasible,since the light source is used sequentially by the different fibers inthe bundle.

In FIG. 8, yet another embodiment of a volume microprobe array 110 isshown. The device includes two optical assemblies, an excitation orsource assembly 111 and a detector assembly 112. Each of the assembliesis interfaced to its own individual fiber bundle 113 and 114,respectively. The individual fibers are organized, in one embodiment, intwo rows 116 and 117, respectively, in a fiber holder 115. When a lineararray is desired, the fibers are organized in two opposing rows, one rowconsisting of the excitation fibers in bundle 113 and the other row ofdetection fibers in bundle 114. When a two-dimensional array is desired,the fibers are organized in alternating rows of excitation fibers anddetection fibers, with a small tilt of such rows relative to each other.The excitation optics 111 includes a light source 118 and focusingoptics 119 that can focus the output of the light source on each fiberin the bundle 113 sequentially. A rotating mirror 120 is used to indexthe light source onto the opening apertures of the fibers in the bundle113. One should appreciate that the input aperture of the excitationfibers can be terminated in an appropriate way to improve collection ofthe light from the rotating mirror. Such termination may include, but isnot limited to, flaring of the input end of the fiber, or termination ofeach fiber with a small compound parabolic concentrator, as is wellknown in the prior art.

In operation, the controller 18 causes the incremental rotation of themirror 120 so as to direct the excitation beam to fibers in bundle 113sequentially. This light then emanates through an excitation field stopat each distal end of the fiber, the field stop being essentially theaperture of each fiber. These field stops are imaged onto a sample 124with objective microlens at the end of each fiber. The distal ends ofboth excitation and detection fibers are terminated into microlensesthat serve as objectives. The excitation and detection fibers may be ata slight angle to each other, and sheared conjugation of theirrespective field stops (fiber apertures) defines the volume elementsprobed. The volume elements in the sample will be a mirror image of thefiber arrangement, namely a row or an array of points, depending on theorganization of the fibers in the fiber holder 115. The distance betweenthe volume elements may be the same as that between the fibers in thefiber holder or may differ from the interspacing of the fibers in thefiber holder, and will depend on the magnification of a relay lens 125.In some embodiments, one can allow for movement of the relay lensrelative to the fiber holder so as to provide magnification (ordemagnification). However, the size of each volume element will also bemodified somewhat.

This configuration allows for the sequential illumination of an array ofvolume elements in sample 124. An excited volume element will emit aresponse to the exciting beam. To ensure that responses that areessentially emanating only from the desired volume element are detected,the responses are collected with a dedicated fiber from bundle 114. Theoptics are configured such that the respective field stops of theresponse fibers (their natural aperture) are each conjugated to therespective field stops of the associated exciting fiber. As a result ofthis conjugation (or, more accurately sheared conjugation, since theexciting and detecting field stops are slightly spaced apart), theexcitation beam has its highest intensity within the sample within thezone of sheared conjugation (the probed volume element), and theintensity declines very rapidly outside the volume element. Furthermore,responses collected by each detection fiber emanate essentially onlyfrom the volume element, and any response collected from adjacenttissues is very small relative to the response obtained from the zone ofsheared conjugation of the excitation and detection field stops.

Since the excitation of the array of volume elements is carried outsequentially, response will be transmitted through the fiber bundle 114sequentially to the detecting optics 112. In a preferred embodiment ofthe invention, the response optics include a receiving rotating mirror123 which directs (sequentially and in synchronism with the excitationmirror 120) the responses through a focusing lens 122 to a detector 121.This assures that stray responses (namely, responses emanating outsidethe zone of sheared conjugation and thus outside the target volumeelement) and collected by adjacent fibers, do not reach the detector. Inthis manner, as before, spatial discrimination is obtained, andsequential detection of responses from specific volume elements isachieved.

In this embodiment, the use of a beam splitter is avoided, and only verysimple optics are used at the distal end of the device. Such a device isparticularly suitable when a distance between the sample and the optics(source and detector) is required, such as in laparoscopic andendoscopic devices. This embodiment has the additional advantage thathigher excitation energies are feasible, since the light sourceresources are not distributed simultaneously over a full array as insome embodiments described above, and in this respect is similar to theembodiment shown in FIG. 7 and described above.

In FIGS. 9 and 10, two additional embodiments of the invention, whichdiffer from each other only in the position in the system of theaddressable light shutters, are shown.

In FIG. 9, a volume microprobe array 130 that includes a light source131, a detector 132, and an optical fiber bundle 133 is shown. Theproximal end of the optical fiber bundle interfaces an addressable arrayof optical shutters 134. The optical shutters are under the control ofthe controller 18. Each fiber in the bundle 113 is positioned in anarray arrangement that corresponds to the addressable light shutterarray. The light source 131 is coupled to the light shutter array via acondenser lens 135 and a shutter array coupling lens 136. As a result,light from the light source is distributed over the light shutter array,and, when one of the shutters is in the open position, light istransmitted to the specific fiber coupled to that specific shutter. Atthe distal end of the fiber bundle, the device has objective optics 137which essentially images each of the apertures 138 of the fibers on asample 139. The distal apertures of the fibers are, in essence, actingas the excitation and detection field stops for each of the volumemicroprobes in the volume microprobe array 130 of this embodiment.Responses to the exciting signals emitted from volume elements in thesample are collected by the fibers through the same objective optics 137and the same fibers through which excitation was carried.

Since the field stops of both the exciting and detecting optics areconjugated within the volume element probed, the excitations andresponses are limited to the individual volume elements probed by eachfiber. In operation, the light shutter array is controlled by thecontroller 18 to sequentially open the light shutters in front of thefiber bundle sequentially in such as way that only one fiber is poweredat any given time. Thus, by the synchronous detection of responses fromfibers that are coupled to an open shutter, a full artificial image ofpathologies in the targeted sample can be constructed. As in some of theembodiments described above, the response is separated from theexcitation by a beam splitter 140 positioned at 45° to the optical axisof the excitation optics and detection optics.

In FIG. 10, a similar volume microprobe array 150 is presented. Theessential difference is that a shutter array 154 is positioned at thedistal end of the fiber bundle. This allows for selecting an array offield stops determined by each of the apertures within the shutter arrayrather than by the individual apertures of the optical fibers.

In some embodiments of the volume microprobe arrays described above, aplurality of detectors corresponding to adjacent full regions of theshutter array are employed. Each detector accepts responses from asubarray of the light shutter array, and thus from the sample. In theseembodiments, data collection is accelerated by the simultaneous openingof a light valve in each of the subarrays in the light shutter array anddetecting the response in their respective detectors. When using thisapproach, care is taken to assure that interferences (or noise) fromresponses outside each specific region are smaller than a preset valueof the expected response from the sample in each region.

In several embodiments described above, an array of light shutters isemployed to sequence the excitation of an array of volume elements inthe sample as well as collect responses from the volume elements. Insome embodiments, each shutter serves as an excitation and detectionfield stop, while in other embodiments other optical elements in thesystem perform the function of the field stop. Such light shutters arewell known in the prior art and have been used in a number of displaydevices, whereby the sequence of opening and closing sets of opticalshutters that are back illuminated provide either a fixed or a timevariable image.

The actual embodiments of such shutters in the prior art can take manyforms. The most widely used light shutter array is an array of liquidcrystal elements having two sheets of polarizer one each on the frontand the back of the array. On each element in the array, a voltage canbe applied. When the voltage is sufficiently high, the liquid crystalcauses rotation of the plane of polarization of light passing throughit. The two polarizers are oriented in such a way that no light passesthrough an element when no voltage is applied. Thus, the polarizers arecross polarized (their relative orientation is 90°, thus the firstpolarizer removes all light polarized in one direction, while the secondpolarizer blocks the light passing through the then inactive liquidcrystal element). When a sufficiently high voltage is applied, the planeof polarization of the light passing through the liquid crystal cell isrotated, so that the second polarizer is essentially transparent to thelight passing through the active liquid crystal cell. The addressing canbe carried out as in the prior art, either as row and columns, so thatonly the sum of voltages applied to both a row and column is sufficientto cause the desired rotation of polarized light. Since the dimensionsof our light shutters are relatively large and the number of shutterssmall relative to the current practice in liquid crystal display, suchaddressing is quite sufficient, and cross talk is minimal andinsignificant in view of the strong spatial discrimination due to theconjugation of the excitation and detection field stops.

When very large arrays are desired, approaches such as used in activematrix liquid crystals display (namely the activation of a pixel throughthe direct switching of an individual transistor at each pixel) can bepracticed as well.

In yet another embodiment, the shutter array consists of ferroelectricelements activated in a manner similar to that of liquid crystal lightshutter arrays. These shutter arrays are useful when the switching ratedesired, namely, the rate of opening and closing a given light shutterin the array, is faster.

In yet another embodiment, the light switching medium is a polymerdispersed liquid crystal (PDLC). In such films, a dispersion of dropletsof liquid crystal is embedded in a polymer having an index of refractionequal to the field oriented index of refraction of the liquid crystaldispersion. When no electrical field is applied, the droplets arerandomly oriented and light is scattered in all directions. Thus theshutter can be considered as closed. When a sufficiently large electricfield is applied to a PDLC element, the liquid crystal droplets orientthemselves with the field and thus, in the direction of the field, theindex of refraction is essentially constant and light passes throughuninterrupted. Thus the shutter is open.

In yet another embodiment, essentially electromechanical shutters areused. Such can be easily implemented with piezoelectric bimorphs, whichwhen actuated bend out of the path of the light and when inactive,assume a straight geometry which blocks light transmission through agiven shutter.

In FIG. 13a, a top view of a light shutter array 310 is shown. Thisshutter array consists of two main elements, a passive base element inwhich an array of perforations 311 and an array 320 of active flags 321are provided. The passive base can be made of an appropriate plastic,metal or even silicon. In the present embodiment, the perforations 311are about 0.1 mm in diameter and are spaced on a grid in which theinterspace between the perforations is about 1.0 mm. It should beunderstood that other dimensions may be selected without deviating fromthe teachings of the invention. The perforations, which arepreferentially slightly conical with their bases at the proximal end andtheir truncated apices at the distal end, serve as receptacles foroptical fibers, each having an external diameter of 0.1 mm. Inproduction, such fibers can first be inserted and cemented in place, andthen the surface of the passive base, with the fibers in place, isoptically polished to ensure that the fibers are flush with the distalsurface of the base and have an acceptable optical finish. The surfacecan then be treated with an antireflective coating so as to minimizeoptical reflections from the distal ends of the fibers, and thus improveboth the illumination and signal collection efficiency.

The array 320 of active flags 321 consists of two sheets ofpiezoelectric material, such as polyvinyl difluoride (PVDF) withmetallization on both sides. The two sheets are first cemented together(for instance with an acrylonitrile compound). Then the metallization isetched, leaving a pattern of rows of electrodes 323 interconnected withcommon leads 322 (in rows) on the top side of the pair of PVDF sheets asshown in FIG. 13a. The electrodes 323 have the same geometry as theflags 321, or can be just a little smaller than the flags. In FIG. 13b,the bottom side of the array 320 of active flags 321 is shown. Themetallization of the bottom side is etched to provide second electrodes324 for each flag, which are interconnected with leads 325 in columns.After both sides of the paired PVDF sheets have been treated to leaverows of electrodes on one side and columns of electrodes on the oppositeside, the flags are formed, the electrodes being congruent on both sides(overlapping but spaced apart by the two sheets of PVDF). The array offlags 321 is created by punching or etching horseshoe-like perforations326 around each of the metallized pairs of opposing electrodes in thearray. It should be apparent to a person trained in the art that onecould choose to first form the flags and then etch away the excessmetallization between the rows and columns of electrodes.

In operation, the application of a voltage to a row of top electrodes323 through the common lead 322 causes the top half (formed by the topPVDF sheet) of the flags 321 in that row to become shorter than in theirrespective unpowered state, while the application of a similar voltage(but of opposite polarity) on a column of bottom electrodes 324 viacommon lead 325, causes the bottom half (formed by the bottom PVDFsheet) of the flags 321 in that column to become elongated relative totheir unpowered state. Let us assume that the appropriate voltages areapplied to a specific row through conductor 328 and none other, and to aspecific column through conductor 327 and none other. Thus, the flag329, which is the only flag at that time having both its top and bottomelectrodes powered, has on its top portion a voltage that causes its tophalf to shorten and has on its bottom portion a voltage that causes itsbottom half to elongate. As a result, flag 329 bends upward and exposesthe perforation under it, allowing illumination to reach the sample andallowing responses from the sample to reach the aperture of the opticalfiber and thus be transmitted to the sensor. All other flags in the rowpowered by the row conductor 328 are devoid of voltage on theirrespective bottom electrodes, and, similarly, all other flags powered bythe column conductor 327 are devoid of voltage on their respective topelectrodes. Thus, only the flag 329 powered simultaneously by the rowconductor 328 and the column conductor 327 is forced to bend upward. Onecan therefore actuate the flags 321 in a PVDF optical shutter array byapplying an appropriate voltage to a given column and sequentially applyvoltage pulses to the rows, or one can randomly activate a flag byapplying the appropriate voltages to its coordinate row and column.

In FIG. 14, a variation of a PVDF based optical shutter array 330 isshown. PVDF flags 332 are structured in a similar fashion to the systemshown in FIGS. 13a and 13B and described above. Specifically, two sheetsof PVDF are cemented back to back, and flags 332 are formed withelectrodes on both sides connected on the top side in columns with leads333 and connected on the bottom side in rows with leads 334. Thisassembly is overlayed on a plate having an array of perforations 331.The flags are oriented at 45° to the main lattice to allow for a greatermovement of the flag. This is important when the fibers have very largenumerical apertures and the beams emanating from the fibers spread at ahigh angle, and the collection angles of responses from the sample aresimilarly large. The operation of this array follows the principlesdescribed above. In particular, the application of a driving voltage toa given column and a given row causes the actuation of the flag on thatcolumn and row.

These are just two examples of embodiments of an optical shutter arrayin which the actuation of the optical shutters is based on movementinduced by piezoelectric bimorphs. In another arrangement, the bimorphsare arranged in rows perpendicular to the base surface of the array, andeach bimorph has a flag (parallel to the plane of the array and thusperpendicular to the bimorph) covering its respective perforation in thearray. The actuation of each bimorph causes movement parallel to thearray surface rather than above the surface. This embodiment is somewhatmore difficult to implement, but has the advantage that smaller bendingof the bimorph is required, particularly when the optical fibers used inthe array possess a large numerical aperture.

In FIG. 15, yet another embodiment of an array of optical shutters isshown. In this embodiment, the array 340 is best produced by techniquesof micromachining from silicon wafers. While a certain order ofdescription of the various elements in the array is followed below, thisorder is not necessarily the order used in the micromachining process.Perforations 341, through which optical fibers are inserted, areprovided in an array. In this embodiment, these perforations are about0.1 mm in diameter and are spaced on a grid of 1.0 mm spacing. Eachperforation is associated with its own shutter 342. The shutter 342consists of a thin flexible arm 343 anchored on one side to the baseplate 344 via an axis 345. On the opposing side of the arm, a flag 346is provided. The flag is sufficiently large to cover its respectiveperforation 341 when the shutter is in the closed position. Two seriesof posts 347 and 348 positioned on opposite sides of the arm 343 areconnected to appropriate electrical leads (not shown). Similarly, theshutter element is connected to its own electrical lead (not shown).

There are a large number of possible variations of this embodiment, anda few of these variations are described here. In one embodiment, thetotal array of optical shutters is manufactured monolithically from asingle wafer. In that case, the arm and flag are machined to be in the"open" position 349. Otherwise, it becomes impractical to etch theperforations. In other embodiments, the array is produced from twopieces cemented together. One piece may contain the array of arms, andthe other piece may contain the array of perforations. Then it ispreferred to have the rest position of the arms in the closed position.The groups of posts 347 and 348 can be on either of the two wafers, butfor practical reasons it is preferred to produce them on the array ofarms. It is also possible to provide a single well-positioned post forthe group of posts 347 and a single well-positioned post for the groupof posts 348. The choice of the specific design depends on the dynamicresponse required from the light shutters in the array.

The operation of the arm as a light shutter is based on theelectrostatic attraction and repulsion generated by the charging anddischarging of various members of the assembly. In operation, the armmay be charged, for instance negatively, and the distal posts 347 may becharged positively to cause the arm to be attracted to this set ofposts. To accelerate this action, the proximal posts 348 can be chargednegatively to cause simultaneous repulsion of the arm. It should beunderstood that actual contact of the moving arm with either group ofposts 348 or 347 is not required. It is preferred to actually avoid suchcontact and in order to accomplish this aim, the whole assembly can betreated to have a thin layer of silicon oxide as an insulation, thusavoiding such contact.

To facilitate the driving of the shutter array, it is preferred to applythe activating voltages in rows and columns, and only the simultaneousactuation of a given column and a given row causes opening of theshutter at the intersection of the selected row and column. This can beachieved in a number of ways. Consider the case where the device is madeof two independent wafers, so that the rest position of the arm can bein the closed state. Thus, when no charges are present on the arm, theoptical shutter is closed. Referring again to FIG. 15, we apply a pulsecharging all the arms in the first row negatively, and through the pairof leads for the first column, a positive charge is applied to the posts347 and a negative charge is applied to the posts 348. The negativelycharged arm in the first row and the first column is repulsed from thenegatively charged posts 348 and is attracted to the positively chargedposts 347, thus opening the optical shutter previously covered by theflag 346. The other arms in the first row are unaffected, since theirrespective posts 347 and 348 are uncharged. Similarly, all arms in thefirst column are uncharged and thus, despite the fact that the posts 347and 348 are charged, the arms do not move, thus leaving the opticalshutters closed. When scanning the whole array, all arms 343 in a givenrow may be kept charged and the posts in adjacent columns may besequentially charged.

The return of the arm to its closed position may be achieved eitherthrough the spring forces in the arm or actively by reversing thecharges on the posts 347 and 348. The selection of a passive return oran active return to the closed position is determined by the dynamics ofthe scanning process. When extremely rapid scanning is desired, reversalof the charges on the posts is preferred, but when the dynamic responsemay be slower, mechanical relaxation to the rest position may bepracticed.

In FIG. 16, another embodiment of a micromachined optical shutter arrayis shown. Here, as in FIG. 15, the array may be monolithically producedor may be assembled from two sub structures. In the base plate, an arrayof perforations 361 having a diameter of about 0.1 mm spaced on a gridwhose points have 1.0 mm spacing is provided. The active elementscomprise flat arms 362 attached to the base plate with a twistable postaround which the arm can rotate. The distal end of the arm issufficiently broad to cover the perforations and thus block the opticalpath to the fibers that are mounted within the perforations. While inFIG. 16 arms having their width gradually expanding to cover theperforation 361 are shown, it should be understood that a narrow arm 362terminated by a wide flag at its distal end, sufficient to cover theperforation, may be provided.

The proximal end of the arm is terminated with a structure 364 generallyperpendicular to the axis of the arm. Two posts 365 protrude from thebase plate, positioned somewhat apart from the structure 364. When thearm is, for instance, charged negatively, and the posts 365 are chargedpositively, the electrostatic attraction causes the arm to rotate andexpose the perforation, thus opening the optical shutter as shown inposition 366. Here as above, the array may be operated by maintaining agiven row (charging the arms 362 in that row) negatively and scanningthe column, which positively charges all pairs of posts 365, to obtainsequential opening and closing of the optical shutter array. As above,the elastic properties of silicon may be relied upon to return the armto its rest position (through the twisting base 363 spring action), orthe charge on the pairs of posts may be reversed before switching to thenext column.

A variety of light sources can be used in conjunction with the arrayvolume microprobes of the present invention. For instance, when thedesired responses are fluorescence responses, one would often use alaser source, such as a nitrogen laser having a wavelength in theultraviolet part of the spectrum, such as 337 nanometers. Whenbackscattering as well as absorption in a broader part of the spectrumis the desired response, the light source is usually a broad spectrumsource such as, but not limited to, a xenon discharge lamp, a halogenincandescent lamp, or any other suitable broad spectrum light source.Furthermore, such a light source can be conditioned with an appropriatefilter to homogenize or otherwise modify the light spectraldistribution. The use of more than a single light source in a givensystem is also contemplated. Thus a volume microprobe array may includea UV laser source to perform fluorescence measurements, as well as awide band light source to perform scattering and absorptionmeasurements. A third light source particularly rich in near infraredradiation can be included as well. In operation, these light sources canbe directed toward the excitation optical assembly in a predeterminedsequence. For instance, a typical UV laser source would operate in apulse mode having a relatively short duration pulse (for instance undera microsecond) and a slow repetition rate. Thus a lapse time betweenexcitation of milliseconds or fractions thereof (often done to avoidoverheating of the laser source) is available between measurements offluorescence responses. During this lapse time, a broadband light sourcecan be directed at the excitation optics, and measurements of theresponse of the target sample to that second light source can bedetected.

Furthermore, to obtain additional diagnostic and analytical informationfrom the volume elements probed, one can obtain Raman scattering datawhich provide molecular structural information on the material probed.The light source or excitation beam can then be a laser within thevisible range of the spectrum. When it is desired to reduce thefluorescence signal generated with an intense beam in the visible partof the spectrum (which masks the much weaker Raman scatteringresponses), one can use a laser in the far red or the near infrared partof the spectrum. Such light sources can be a HeNe laser at 633 nm, or aGaAlAs diode or laser diode at 783 nm or even a Nd:YAG laser at 1064 nm,as well as other near infrared diodes or laser diodes. In someembodiments of the invention, when multiple light sources are used,multiple detectors can be used as well. Each is designed to be optimizedfor the spectral response and response intensity anticipated. In suchcases, the timing of the excitation from the plurality of sources andthe responses from their associated detectors is controlled by thecontroller 18.

In FIG. 11, a typical volume microprobe array 170 with its associatedelectronic modules and computing modules is shown. The optical system issimilar to that shown in FIGS. 9 and 10 and described above, except thatthe beam splitter is positioned at the distal end of the optical fiberassembly, and in lieu of using the light shutter array for both theexcitation and detection optics, an array of detectors is used for thespatial discrimination of the responses, rather than an array of lightshutters. Specifically, the volume microprobe 170 includes a dataprocessing and system control unit 171 and an optical system 172. Theoptical system includes at least one light source 173. Lenses 174 and175 are interposed between the light source and a light shutters array176 so as to image the light source onto the array. Interposed betweenlens 174 and 175, a device 176 can be included to condition the spectraldistribution of the light source. Such a device can be a filter that isdesigned to modify the normal spectral distribution of the light source,which may include parts of the spectrum at intensities that are greaterthan other parts, and thus normalize the spectral distribution of theexciting beam. The element 176 can be a plurality of filters mounted ona rotating filter wheel, so as to interpose different type of filters(or no filter) in the exciting beam path.

Also interposed between the two lens 174 and 175, a second device 177can be included to modulate the exciting beam in time and in intensity.Such a scheme can be used to improve the signal-to-noise ratio of thedetection system by synchronizing the modulation and detection throughan appropriate phase locked amplifier (not shown), which is part of theelectronics system 171 (indicated as control arrows 191 and 193).Similarly the timing of the light source 173, including the sequencingof a plurality of light source or the pulse rate and pulse width of a UVlaser source, is also under the control of the controller 201 asindicated by the control arrow 192. The light shutter array 176 iscoupled to an optical fiber bundle 178 in such a manner that each fiberwithin the bundle is coupled to a given light shutter in the array. Thedistal ends of the fibers within the bundle 178 are arranged in the samearray configuration as the proximal ends so as to maintain the samearray geometry. The aperture of the individual optical fiber determinesthe field stop of the excitation optics in this embodiment. The lightshutters within the array 176 are under the control of the controller201 via a control line 200, and in operation, the controllersequentially opens light shutters so as to provide an excitation beamsequentially to all fibers in the array.

Light emanating from the distal ends of the fibers in the bundle isimaged onto a sample 185 with objective optics 179. In the embodimentshown in FIG. 11, a beam driving mirror 184 is provided, the function ofwhich is to select, within the sample, the desired area from which anarray of volume elements is to be analyzed. The tilt of the directingmirror 184 is controlled by a joy stick 187, which can be operatedmanually, or be under the control of the controller 201 via control line196.

Responses from the target array of volume elements within the sample 185are redirected by the directing mirror 184 to the objective optics 179,and a beam splitter 180 is utilized to separate the excitation beam fromthe responses. Since the illumination of volume elements within thetarget array is sequential, at any time, only responses from a givenvolume element are received by the detector assembly. The detectorassembly contains an array of detectors 183, and the respectiveapertures of each detector element within the array also serve as thefield stops of the detection optics. Since both the excitation opticsand the field stops of the detection optics are conjugated within thetarget volume element in the sample, we ensure that detection ofresponses emanating essentially only from each volume element arerecorded for each volume element in the sample.

The detector assembly also contains additional traditional opticalelements, such as a spectral filter 181, whose function is to eliminatefrom the responses undesired parts of the spectrum. For instance, whenthe excitation beam is a nitrogen laser and the desired responses arefluorescence emissions, the filter blocks any reflections of theexcitation beam and prevents their registration as responses. A spectralanalyzer 182 is also included to determine the spectral distribution ofthe responses. The detector array is under the control of the controller201 via a control line 194 so as to ensure the synchronization ofexcitation and response detection from each volume element in the targetsample.

The detector assembly, or in some embodiments a specific element of theassembly such as an objective lens, can be caused to move in a directionparallel to the optical axis of the assembly with a driving mechanism186 under the control of controller 201 (through control line 197), soas to adjust the z position, or depth, of the volume elements probed bythe array microprobe system, in a manner similar to that describedabove.

Signals from the detector, representing optical responses, are directedto a signal processing unit 202, which then transfers the data to ananalog to digital converter 203 for further data conditioning in a datapreparation module 204. The data representing responses (and tagged toassure that the processor recognizes data from various volume elements,which is achieved with a control line 199 from the controller 201) arethen treated in a calibrator/scaler 205 to normalize the data. This isachieved by monitoring the output of the light source and renormalizingdata for variations in the output of the source via line 220.

The control and data processing unit 171 contains a memory unit 210 inwhich calibration and scaling constants 208 are stored as well ascorrelation transform matrices 209, as further described below. Datafrom the system are converted to diagnostic information by a computer211 and displayed, either as diagnostic values or as artificial maps ona display station 212. The computer has memory (resident or removable)in which data can be stored and retrieved for future analysis off line.

In general, the invention is intended to operate, at least partially, torecord and generally also compile and analyze the responses it collects.In some low cost embodiments of the instant invention, only diagnosticprediction of pathologies is provided. In this case, the system isequipped with a library of correlation transform vectors or matrices forspecific diagnostics, and the system only registers the signals I_(ij)(response intensities at a specific wavelength, i, for a specific volumeelement j) and calculates functions F(I_(ij)) required to provide adiagnostic score C_(j), for an array of volume element j, as is furtherdescribed below.

The output from detector 183 is fed to a data processor 206 afterpreprocessing in signal processor 202, analog to digital converter 203and data preparation module 204. Data processor 206 can process theoutput from detector 183 or it can store the data in memory unit 210 forprocessing at a later time. The computer 211 can also provide theability to compare a first data set obtained from detector 183 with asecond data set obtained from memory unit 210, or to perform comparativestudies of various volume elements within an array of volume elementsmeasured at any given time, thus providing for spatial correlation ofvolume elements within a given sample. For example, data processor 206can calculate correlations between a first data set representative ofthe material being probed and a second data set in memory unit 210. Inaccordance with a preferred embodiment of this aspect of the invention,the second data set may be a library of optical response data or amathematical model abstracted from such a library, as described below inthe section entitled, "Methodology and Operation."

Memory unit 210 can be used to store a large body of data aboutparticular materials. For example, memory unit 210 can store dataconcerning the characteristics of light which has interacted with aparticular type of biological tissue, or memory unit 210 can store dataconcerning the characteristics of light emitted, particularlyfluorescence, by particular types of biological tissues in response toexcitation by each of a set of wavelengths of light, or can store suchspectra indexed by tissue depth, or other complex multidimensionalspectra derived from a prior set of observations.

Memory unit 210 can further store information associating particularcharacteristics of light obtained from a biological tissue sample with aparticular diagnosis. For example, the ratio of light reflected at onewavelength to light reflected at a second reference wavelength can beassociated with cancerous tissue growth as in certain knownobservations, or may be associated with a clinically relevant conditionsuch as a thickening of one layer of tissue, a precancerous metabolicchange, or a malignancy, based on correlation with the spectral libraryand previous clinical characterizations. Thus, correlation withannotated or stored digitized spectra may provide a diagnostic judgment,even without the identification of any specific individual spectralfeatures, such as peaks or absorbance bands, that have been required fordiagnosis in the past.

While in the embodiments shown herein, for example in FIG. 11, thedetector 183 is shown accepting responses from the specimen after beingtreated trough a spectral analyzer 182, it should be clear that thespectral analyzer can be replaced with either a temporal interferometer(such as a Michelson interferometer) or a spatial interferometer (suchas a Sagnac interferometer). The resulting interferogram may thenprovide the Fourier transform of the optical responses obtained fromeach volume element probed for subsequent data analysis as describedelsewhere in this application.

Similarly, when performing Raman spectroscopy, particularly whenselecting for an excitation beam a source in the near infrared, wherethe intensity of the Raman scattering is greatly reduced, one can imposein the response path, in lieu of an interferometer, a Hadamardencodement mask consisting of a multi-slit array, in order to obtain viaHadamard transform of the data the Raman spectral response of the probedvolume elements.

METHODOLOGY AND OPERATION OF THE VOLUME MICROPROBE ARRAY

In the prior art, spectral and chemical analysis of complex andheterogeneous matrices with good localization of such analysis washindered by the inability to limit the response obtained from suchmatrices from regions with a high degree of homogeneity. A large groupof microprobes was thus developed to handle this problem, and indeed,electron microscopes and ion microprobes and various other devicescapable of providing analytical information exist, both morphologicaland to some extent chemical (mostly elemental) on a point by point oreven through sections (such as in the ion microprobe) of a specimen.Unfortunately, these methods all require the placement of the sample invacuum and the eventual destruction of the specimen, and furthermorethese methods are not conducive to the analysis of organic materials. Invivo microprobe analysis of biological tissue has requirements that aresomewhat different from those of classical microprobes. Particularly, itis not desired to have a resolution greater than the typical dimensionsof differentiated tissues, but it is required to have analytical toolsthat can be operated by personnel without specific training in theanalytical arts, such as physicians, process control personnel and otherprofessionals. The use of the present invention allows for microprobingof samples and biological tissues in vivo, and enables the spatialdelineation of compositional, morphological and pathological features ofsuch specimens. There are numerous approaches by which the data fromsuch array volume microprobe can be used, and without limiting the scopeof the instant invention, we describe herein some of these approaches.

In one embodiment of the present invention, responses from an array ofvolume elements, which represent the interactions of the material withineach of said volume elements with the exciting radiation, or at leastcontain specific signatures of such interactions, are presented in termsof received light intensities for various wavelengths, or as is known inthe art, as a spectrum of the response. A researcher trained in thespecific analytical art can then use these spectra to deduce importantinformation about each of the volume elements in the array from hisknowledge of the exciting radiation and the modes of interactions of theradiation with his target material. A variety of analytical tools, suchas software programs designed to conduct spectral peak fitting, orspectral deconvolution, can be used to further increase the researcher'sbasic understanding of such interactions and to provide the researcherwith information on the chemical, morphological and physiological natureof the target volume elements in the array, since the responsescorrespond each to a specific volume element in the array probed. Thisin accordance with basic principles known in the art, except that thedata provided to the researcher are derived from a well-defined volumeelement and thus interferences and response weakening due to parasiticresponses and interferences originating outside the target volumeelements no longer hinder the researcher's ability to differentiatespecific features within a largely heterogeneous sample. Thus, the arrayvolume microprobe of the present invention can be used to performclassical spectroscopical analysis, fluorescence analysis, Ramanscattering and other parametric or characterizing analysis whichinvolves the measurement of the responses of each volume element in thearray to a localized radiation while limiting the observed responses toessentially each of the volume elements in the array only at any giventime.

In another embodiment of the present invention, directed to users thatdo not possess the technical skills to derive meaningful conclusionsfrom raw responses observed, the system is equipped with a library ofcorrelation transforms dedicated to the user's special needs, so thatthe system is essentially pre-calibrated for specific analytical tasks.The method of calibrating the array volume microprobe is furtherdetailed herein.

For simplicity of the following description, we assume that the goal ofthe method is to calibrate an array volume microprobe for the diagnosisof the presence or lack thereof of tissues that are affected by certaincancer and that are accessible to optical visualization, either on theexternal skin, or in the cervix, or in other cavities that areaccessible via endoscopes or laparoscopes, such as the various segmentsof the gastrointestinal tract (starting from the mouth, through theesophagus and the stomach, and by rectal examination the colon), orvarious organs in the peritoneal cavities that are accessible viaexploratory laparoscopy. In many of these situations, a physician whichis not a trained spectroscopist views the suspected tissues, and whendiscoloration or other morphological abnormalities are present, samplesfrom such areas are excised and sent to a pathological laboratory formicroscopic examination of the tissues to determine the presence or lackthereof, as well as the stage, of possible cancer. It would be extremelyuseful if, during the visual examination, a diagnostic scoring todetermine the nature of the suspected pathology of the suspicious targettissue was available, so that immediate action could be taken, ifnecessary, and to avoid unnecessary excision of tissue for biopsies.When calibrated as described below, the array volume microprobe of theinstant invention will enable the automated diagnostics of such viewedtissues by a physician, provide an artificial image of the pathology andits extent, without the need to examine such tissues under themicroscope by another professional pathologist.

FIG. 12 is a diagram 300 showing the various steps undertaken in thecalibration and then the use of the array volume microprobe. In order tocalibrate an array volume microprobe 301 for a specific pathology, atraining set 302 of specimens for the specific pathology is firstselected. The term training set will be used herein to denote a group oftissue specimens on which very exacting cytological and pathologicaldetermination of the state of each specimen was conducted in apathological laboratory, denoted by the step 303. Furthermore, prior toexcision for such biopsies, each specimen in the training set wassubjected, in vivo, to an exacting study with the microprobe array 301of the present invention. For the purpose of this description, let usassume that the target volume elements in the training set (thosetissues that are later subjected to a pathological laboratorydetermination of their respective pathological states) are excited withboth a laser UV source and a broad band white light source. To assuregood spatial correlation between the excised tissues and the volumeelements examined, during calibration, the array is used with only asingle shutter open, or a special single channel non imaging volumemicroprobe can be used. Let the intensities of the responses to the UVand white light excitations of the targeted volume element within thespecimen j be J_(uj) and I_(ij) respectively, where u and i are centralwavelengths within spectral bands of the spectral responses to the UVand to the white light excitations, respectively. These data are storedin memory (for instance memory unit 210 in FIG. 11) for future analysisand determination of the master calibration at step 304. The volumeelements in the training set are excised after recording the responsesobtained with the non imaging volume microprobe, and pathologicaldeterminations of the state of each specimen are recorded in the form ofscores C_(j), where j is the identity of the specimen and C_(j) is anumber selected according to the specimen state on a monotonic scoringscale, for instance 0 to 10, where zero denotes normal tissues and 10fully entrenched and deep cancerous tissues. Since this training setwill calibrate non imaging volume microprobes for future determinationsof the presence or lack thereof of such pathologies, it is importantthat great care is taken at arriving at an objective determination ofthe pathological state of the training set. In such cases, the samesamples are examined microscopically by a number of independentpathologists in a blind experiment, and only those specimens for which aminimum agreement between the various pathological results exists, areincluded in the training set.

Once the scores C_(j) of the specimen in the training set have beencarefully determined, and the medical records of the patients associatedwith samples (volume element) in the training set are recorded (morethan one volume element per patient can be included in the training set,however, it is best to include a variety of patients in a training setfor a given pathology), the values of I_(ij) and J_(uj) previouslystored in memory unit 210 are used to set up a set of n correlationequations (n would be the number of volume elements in the trainingset):

    Σa.sub.i F(I.sub.ij)+Σb.sub.u F(J.sub.uj)+Σc.sub.s G(M.sub.sj)=C.sub.j                                       (1)

The bandwidths around the wavelengths i and u of the responses to whitelight and UV light, respectively, are usually between 5 and 50 nm,depending on the spectral resolution achievable or desirable in thesystem's detection monochromator or spectrograph (element 182 in FIG.11).

The selection of the functions F depends to some extent on the nature ofresponses received. When almost featureless spectral responses (namely aspectral response which is relatively smooth and changes slowly with thewavelength) are received, then one often selects the intensities, ornormalized intensities, of the responses namely, F(I_(ij))=I_(ij) orF(I_(ij))=I_(ij) /K, respectively, where K is either the maximumresponse in the received spectrum or the response at a predeterminedwavelength (in biological tissues, often a response associated with thepresence of water or hemoglobin). When the spectrum expected contains anumber of sharper features, one often can use F(I_(ij))=(dI_(ij)/dλ)I_(ij), where λ is the wavelength. Of course, it is best to use thesame function F for the responses to both UV excitation J_(uj) and whitelight excitation I_(ij).

The functions G(M_(sj)) are included to allow for the impact on theobserved responses of the patient's specific "medical history", andusually includes parameter such as sex, age, race, and presence or lackthereof of systemic pathologies such as hypertension, diabetes etc. Inmany situations, part or all the coefficient c_(s) are nil, and thesefactors have no impact on the calibration, but in special cases, thesefactors play a role and are included here for completeness.

A computer is now used at step 304 to perform a regression analysis tominimize the number of wavelengths i and u (and s which are "artificialwavelengths" representing medical history) used to obtain a validcorrelation and to solve the set of minimized equations (1) for thecorrelation constants a_(i), b_(u) (and c_(s)). This regression analysisis performed using the n equations obtained experimentally, using inessence the correlation constants as unknowns, for which a solutionhaving the best correlation is sought. The minimization is carried outto extract those wavelengths at which the responses contain independentrelevant information that correlates the responses I_(ij) and J_(uj) tothe scores C_(j). It should be appreciated that during the calibrationprocess, a greater amount of data is collected than absolutelynecessary, and much of these data are interrelated. To obtain asufficiently good correlation, only responses that are independent fromeach other are necessary, and thus the process of minimization ofspectral responses in equations (1) is carried out. This minimizationwill also allow, during actual diagnostic use of the non imaging volumemicroprobe, the taking of a minimal set of responses and thus willaccelerate the procedure.

The methods used for obtaining the minimal set of wavelengths and theassociated correlation coefficients a_(i) and b_(u) are well known inthe prior art and include multivariant linear regression analysis andunivariant linear regression analysis. Other statistical tools, such asneural networks analysis, are also available and can be used for thispurpose.

In general, we can term the values I_(ij) and J_(uj) the responses ofthe volume element to white light and UV excitation, respectively. As wehave mentioned, other responses may be used to characterize a volumeelement in a sample. We therefore term all responses which are responsesfrom volume elements that correlates with certain pathologies asresponses R_(ij). As mentioned above, we found that it is sometimesadvantageous to include as part of the responses R_(ij) otherinformation about a volume element (or the volume element's host) whichwas not determined with the help of the non imaging volume microprobebut still contributes to improvement in the correlation between theobserved responses and the pathologies diagnosed. Such information mayinclude general classification of the subject in which the volumeelement resides, such as, but not limited to sex, age, race, othersystemic pathologies and weight. Such information, when its inclusion inthe regression improves the confidence level of the regression, can beincluded as additional artificial responses R_(ij) (in lieu of thefunctions G(M_(sj))). The index i therefore represents the type ofresponse obtained, whether it is obtained with the non imagingmicroprobe (one or more types of responses as well as the spectral bandfrom which the response is registered) or by other means.

The set of equations (1) from which the correlation coefficients arederived can thus be simplified to be:

    Σa.sub.i F(R.sub.ij)=C.sub.j                         (2)

For simplicity, the ordered values a_(i) can be termed the correlationvector (a) for pathology C, and the ordered responses R_(ij) can betermed the response vector (R_(j)) for volume element j in the trainingset. The functional response vector (F(R_(j))) is similarly defined asthe ordered functions of the elements of the responses in the responsevectors (R_(j)). Similarly, the ordered scores C_(j) can be termed thepathology score vector (C) for the training set. The process ofcalibrating the array microprobe for a given pathology C consiststherefore of obtaining all the response vectors (R_(j)) and theircorresponding pathology score vector (C) and from these data, aftergenerating the functional response vector (F(R_(j))), obtaining aminimal correlation vector (a), which is the calibration vector of thenon imaging volume microprobe. As can be seen, the calibration isidentical to the calibration designed for the non imaging volumemicroprobe of copending application Ser. Nos. 08/510,041 and 08/510,043.The calibration for a number of different pathologies can be stored in acalibration library 305 for future use on unknown specimens. Eachmicroprobe array includes a correlation engine 307 which can takecalibration vectors from the calibration library 305 and responsevectors obtained from the microprobe array and other sources such asmedical records 308 and reconstruct for the response vector a value C ofthe observed pathology. Since in the various embodiments of theinvention the different optical channels representing excitation andresponses from given volume elements are equivalent, a singlecalibration (for a given pathology) suffices.

When we now want to determine the nature and distribution of a pathologyin a target specimen, which is outside the training set, or an unknownspecimen 306, and for simplicity let us term each such volume element inthe array k(x,y,z), delineating its x, y and z coordinates. The responsevectors (R_(k) (x,y,z)) are registered by the instrument on the volumeelement k(x,y,z), and to the extent that some of the responses R_(ik)are artificial responses (such as sex or race as mentioned above), theseare entered into the correlation engine part of the microprobe array andthe score for the pathology for volume element k(x,y,z), C_(k) (x,y,z),is predicted by obtaining the product of the correlation vector (a)found earlier with the functional response vector (F(R_(k) (x,y,z))),namely: C_(k) (x,y,z)=Σa_(i) F(R_(ik) (x,y,z)). Thus the use of thecalibrated microprobe array on an array of volume elements k(x,y,z),whose pathological state C_(k) (x,y,z) is unknown, allows for theimmediate and automatic diagnosis of the pathology in volume elementk(x,y,z). This procedure is repeated for all volume elements in thearray, and the set of values C_(k) (x,y,z) for all volume elements inthe array can now be presented on a display 309, either as numericalvalues or as artificial images of the array examined. Normal methods ofthree-dimensional image handling and manipulation can thus provide thephysician with an insight as to the nature, extent, severity andpenetration depth of suspected pathologies. This reduces the number ofunnecessary biopsies required and provides the physician with immediateinformation on which he can act during the examination.

It should be appreciated that the functions F(R_(ik) (x,y,z) can bederived from the Fourier Transforms obtained from the responses, eitherwith a temporal interferometer such as a Michelson interferometer orwith a spatial interferometer such as a Sagnac interferometer. It iseven possible to use the interferograms themselves in lieu of theFourier transform generated from them. Similarly, when probing formolecular structural information on the probed elements, one uses forthe functions F(R_(ik) (x,y,z) the values at various wavelengthsobtained from the Hadamard transform of the Raman spectral response.

It should be appreciated by persons trained in the art that, as in ourcopending applications, microprobe arrays of the invention can becalibrated to diagnose a plurality of pathologies P_(m), where m denotesa specific pathology. When used in this fashion, the task of calibratingthe instrument for this plurality of pathologies consists as before ofobtaining for a training set j, responses R_(ij) and pathological scoresP_(mj), where i is the bandwidth of the response or the type ofartificial response, j is the volume element or the specimen in thetraining set and P_(mj) is the score for pathology m on specimen j.During calibration, we obtain a number of correlation vectors (a_(m)),each for the specific pathology m. In operation of the calibrated nonimaging volume microprobe, the correlation vector (a) mentioned above isnow replaced with a correlation matrix {a} whose elements are a_(im),the functional response vector (F(R_(k))) for an uncharacterizedspecimen, k, is replaced with the matrix {F(R_(k))} whose elements areF(R_(imk)) and the diagnostic results are given as a vector (P)_(k)whose elements are P_(mk) by obtaining the product of the correlationmatrix {a} with the functional response matrix {F(R_(k))}.

It should also be appreciated that in the practical embodiment of thismethod of analysis, the correlation created will use the same responses(if not all of them at least some of them) for different pathologies.Thus only a response vector (R_(k)) (having elements R_(ik)) isrequired, which includes the minimal set of responses from volumeelement k to obtain diagnostic scores P_(mk). The matrix {a} can also betermed the correlation transform matrix, since it transforms one set ofmeasurable (or observable) values, to another set of numbers or values,which are the desired pathological scores. This is achieved bymultiplying the correlation transform matrix, {a}, with the vector(F(R_(k))), the functional response vector, to obtain a transformationof the response vector (R_(k)) to a diagnostic score vector (P)_(k).

The correlation transform method exploited herein, of predictingdiagnostic or analytic information on an unknown specimen by correlatingoptical responses of a training set to independent determination of thediagnostic or analytic data on the training set has been shown byRosenthal to work well on artificially homogenized samples that arelarge enough to provide a set of responses possessing a largesignal-to-noise ratio. It is surprising that the expanded method of theinstant invention yields good correlation on very minuscule volumeelements in vivo. In classical spectroscopy, for instance, as practicedby Alfano, spectra or optical responses of diseased tissues are comparedto similar spectra or responses of healthy tissues to attempt adiagnostic reading on the target tissue. This method fails to workbecause of the large variations encountered between subjects and thenature of the tissue examined. When using our correlation transformapproach, we purposefully avoid using comparison of spectral responsesin a target tissue to the responses of any existing (healthy orpathological) tissue, since no one specific tissue can represent all thevariations encountered between subjects. Such subject-to-subjectvariations cause spectral distortions that invariably weaken the abilityof the prior art to obtain robust diagnostic determination ofpathologies. Furthermore, our inclusion of non optical responsestogether with optical responses, as part of the correlation transformalgorithm, in essence builds a completely artificial model (based on thetraining set) of the pathology, which by itself is never reproduced inany one subject or tissue. Finally, this novel approach, coupled withthe spatial filtering of the optical responses to a small volumeelement, thus avoiding response integration over heterogeneous tissues,makes it possible to obtain valuable artificial images of pathologiesheretofore not feasible.

While the invention has been shown and described having reference tospecific preferred embodiments, those skilled in the art will understandthat variations in form and detail may be made without departing fromthe spirit and scope of the invention.

What is claimed is:
 1. Apparatus for determining a characteristic of asample of material by the interaction of electromagnetic radiation withthe sample, comprising:a source of electromagnetic radiation;illuminating optics for sequentially illuminating a plurality of volumeelements in the sample with an intensity distribution in the sample thatdrops off substantially monotonically from a first region in a firstoptical path; collecting optics for collecting electromagnetic radiationemanating from each of said volume elements, said collecting opticscollecting said electromagnetic radiation emanating from each of saidvolume elements with a collection distribution that drops offsubstantially monotonically from a second region in a second opticalpath, said first and second regions at least partially overlapping ineach of said volume elements, said illuminating and collecting opticseach having respective field stops whose dimensions are large comparedto a quotient of wavelength of said electromagnetic radiation divided bya working numerical aperture of said illuminating and collecting optics,respectively, measured from said respective field stops; and a detectorfor detecting the collected electromagnetic radiation emanating fromeach of said sequentially illuminated volume elements to produce aresponse representative of said characteristic in each of said volumeelements.
 2. Apparatus as defined in claim 1 wherein at least one of theilluminating and the collecting optics comprises means for determiningsaid characteristic from a three dimensional array of said volumeelements.
 3. Apparatus as defined in claim 1 wherein the field stops ofsaid illuminating optics comprises an array of individually controllableilluminating optical shutters for sequentially illuminating said volumeelements.
 4. Apparatus as defined in claim 3 wherein the field stops ofsaid collecting optics comprises an array of individually controllablecollection optical shutters for sequentially collecting electromagneticradiation emanating from each of said volume elements.
 5. Apparatus asdefined in claim 1 wherein said illuminating optics comprises an arrayof individually controllable illuminating elements for sequentiallyilluminating said volume elements and said collecting optics comprisesan array of individually controllable collection elements forsequentially collecting electromagnetic radiation emanating from each ofsaid volume elements.
 6. Apparatus as defined in claim 1 wherein theilluminating optics, the collecting optics and the detector includemeans for producing a response representative of a characteristic ofbiological tissue.
 7. Apparatus as defined in claim 1 wherein saidsource, said illuminating optics, said collecting optics and saiddetector are configured for determining said characteristic in vitro. 8.Apparatus as defined in claim 1 wherein said source, said illuminatingoptics, said collecting optics and said detector are configured fordetermining said characteristic in vivo.
 9. Apparatus as defined inclaim 1 wherein said detector includes means for producing a responserepresentative of at least one pathology.
 10. Apparatus as defined inclaim 9 further including means for presenting the response as an imageof the spatial distribution of said at least one pathology. 11.Apparatus as defined in claim 1 wherein said detector includes means forproducing a response representative of cancer.
 12. Apparatus fordetermining a characteristic of a sample of material by the interactionof electromagnetic radiation with the sample, comprising:a source ofelectromagnetic radiation; an optical assembly for sequentiallyilluminating a plurality of volume elements in the sample with anintensity distribution in the sample that drops off substantiallymonotonically from a first region in a first optical path and forcollecting electromagnetic radiation emanating from each of said volumeelements, said optical assembly collecting said electromagneticradiation emanating from each of said volume elements with a collectiondistribution that drops off substantially monotonically from a secondregion in a second optical path, said first and second regions at leastpartially overlapping in each of said volume elements, said opticalassembly comprising at least one array of field stops whose dimensionsare large compared to a quotient of wavelength of said electromagneticradiation divided by a working numerical aperture of said opticalassembly, measured from said field stops; and a detector for detectingthe collected electromagnetic radiation emanating from each of saidsequentially illuminated volume elements to produce responsesrepresentative of said characteristic in each of said volume elements.13. Apparatus as defined in claim 12 wherein said array of field stopscomprises a single array of individually controllable optical shuttersfor sequentially illuminating said volume elements and for sequentiallycollecting electromagnetic radiation emanating from each of said volumeelements, wherein said first and second optical paths are the same. 14.Apparatus as defined in claim 13 wherein said array of optical shutterscomprises an array of individually controllable liquid crystal shutterelements.
 15. Apparatus as defined in claim 13 wherein said array ofoptical shutters comprises an array of individually controllable polymerdispersed liquid crystal shutter elements.
 16. Apparatus as defined inclaim 13 wherein said array of optical shutters comprises an array ofindividually controllable ferroelectric shutter elements.
 17. Apparatusas defined in claim 13 wherein said array of optical shutters comprisesan array of individually controllable piezoelectric bimorph shutterelements.
 18. Apparatus as defined in claim 13 wherein said array ofoptical shutters comprises a micromachined array of individuallycontrollable, electrostatically movable shutter elements.
 19. Apparatusas defined in claim 13 wherein said optical assembly further includes anoptical objective between said array of optical shutters and the sample.20. Apparatus as defined in claim 19 wherein said optical objectivecomprises a single objective lens aligned with said array of opticalshutters.
 21. Apparatus as defined in claim 19 wherein said opticalobjective comprises an array of microlens elements respectively alignedwith said optical shutters.
 22. Apparatus as defined in claim 13 whereinsaid array of optical shutters is subdivided into noninterfering zonearrays and electromagnetic radiation is collected simultaneously fromsaid noninterfering zone arrays.
 23. Apparatus as defined in claim 13wherein said array of optical shutters comprises a plurality of rows andcolumns of shutter elements.
 24. Apparatus as defined in claim 13wherein said array of optical shutters comprises an array of radiallydistributed shutter elements.
 25. Apparatus as defined in claim 13wherein said array of optical shutters comprises a linear array ofshutter elements.
 26. Apparatus as defined in claim 13 wherein saidarray of optical shutters comprises a circumferential array of shutterelements.
 27. Apparatus as defined in claim 13 wherein said detectorcomprises a plurality of detector elements corresponding to said opticalshutters or to groups of said optical shutters.
 28. Apparatus as definedin claim 12 further including means for moving at least a portion ofsaid optical assembly with respect to the sample so as to vary thelocations of said volume elements within the sample along the opticalaxis of said first and second optical paths.
 29. Apparatus as defined inclaim 12 wherein said array of field stops comprises an array ofindividually movable micromirrors, each of said micromirrors beingmovable between an active position for directing illumination from saidsource to the sample and for directing collected electromagneticradiation from the sample to said detector, and an inactive position.30. Apparatus as defined in claim 12 wherein said array of field stopscomprises an array of individually movable micromirrors, each of saidmicromirrors comprising an off axis segment of a paraboloid ofrevolution, said micromirrors being movable in pairs between activepositions and inactive positions, one micromirror of an active pairdirecting illumination from said source to the sample and the othermicromirror of the active pair directing electromagnetic radiationemanating from the sample to said detector.
 31. Apparatus as defined inclaim 30 wherein micromirrors of a first group of said micromirrorssequentially direct illumination from said source to the sample andmicromirrors of a second group of said micromirrors sequentially directcollected electromagnetic radiation from the sample to said detector.32. Apparatus as defined in claim 30 wherein said array of field stopsfurther comprises means for moving each of said micromirrors between anillumination position for directing illumination from said source to thesample and a collection position for directing collected electromagneticradiation from the sample to said detector, wherein each of saidmicromirrors is used for illumination and collection at different times.33. Apparatus as defined in claim 12 wherein said optical assemblycomprises a bundle of optical fibers and an optical fiber switchingdevice for sequentially activating each of said optical fibers fordirecting illumination from said source to the sample and for directingcollected electromagnetic radiation from the sample to said detector.34. Apparatus as defined in claim 12 wherein said optical assemblycomprises a bundle of optical fibers and an array of optical shutterspositioned at one end of said bundle of optical fibers so that saidoptical shutters are respectively aligned with said optical fibers, saidarray of optical shutters sequentially illuminating said volume elementsand sequentially collecting electromagnetic radiation emanating fromeach of said volume elements.
 35. Apparatus as defined in claim 12wherein said detector comprises a single optical detector for detectingcollected electromagnetic radiation from each of said volume elements.36. Apparatus as defined in claim 12 wherein said source comprises alaser source.
 37. Apparatus as defined in claim 12 wherein said sourcecomprises a nitrogen laser.
 38. Apparatus as defined in claim 12 whereinsaid source comprises a broad spectral band light source.
 39. Apparatusas defined in claim 38 wherein said source comprises a xenon dischargelamp.
 40. Apparatus as defined in claim 38 wherein said source comprisesa halogen incandescent lamp.
 41. Apparatus as defined in claim 12wherein said source comprises an ultraviolet wavelength source. 42.Apparatus as defined in claim 12 wherein said optical assembly includesan optical filter for tailoring the spectrum of the illumination. 43.Apparatus as defined in claim 12 wherein said source comprises aplurality of light sources and means for activating said light sourcesat different times.
 44. Apparatus as defined in claim 12 wherein saidoptical assembly further includes means for modulating the illuminationof the sample.
 45. Apparatus as defined in claim 12 wherein saiddetector comprises means for detecting natural fluorescence of tissueafter illumination by a narrow wavelength excitation.
 46. Apparatus asdefined in claim 12 wherein said detector comprises means for detectingresponses produced by selectively absorbed dye in pathological tissue.47. Apparatus as defined in claim 12 wherein said detector comprisesmeans for detecting responses produced by Raman scattering. 48.Apparatus as defined in claim 12 wherein said detector comprises meansfor detecting a combination of backscattering and reflection from saidvolume elements.
 49. Apparatus as defined in claim 12 wherein said atleast one array of field stops comprises an array of individuallycontrollable illuminating optical shutters for sequentially illuminatingsaid volume elements and an array of individually controllablecollection optical shutters for sequentially collecting electromagneticradiation emanating from each of said volume elements, and wherein saidoptical assembly further comprises illuminating light conditioningoptics for directing illumination from said source to said array ofilluminating optical shutters, an illuminating objective for focusingillumination on said volume elements, a collection objective forfocusing said collection optical shutters on said volume elements andcollection light conditioning optics for directing said collectedelectromagnetic radiation from said array of collection optical shuttersto said detector.
 50. Apparatus as defined in claim 12 wherein said atleast one array of field stops comprises an array of individuallycontrollable illuminating optical shutters for sequentially illuminatingsaid plurality of volume elements and an array of individuallycontrollable collection optical shutters for sequentially collectingelectromagnetic radiation emanating from each of said volume elements.51. Apparatus as defined in claim 50 wherein said array of illuminatingoptical shutters and said array of collection optical shutters eachcomprises an array of individually controllable liquid crystal shutterelements.
 52. Apparatus as defined in claim 50 wherein said array ofilluminating optical shutters and said array of collection opticalshutters each comprises an array of individually controllable polymerdispersed liquid crystal shutter elements.
 53. Apparatus as defined inclaim 50 wherein said array of illuminating optical shutters and saidarray of collection optical shutters each comprises an array ofindividually controllable ferroelectric shutter elements.
 54. Apparatusas defined in claim 50 wherein said array of illuminating opticalshutters and said array of collection optical shutters each comprises anarray of individually controllable piezoelectric bimorph shutterelements.
 55. Apparatus as defined in claim 50 wherein said array ofilluminating optical shutters and said array of collection opticalshutters each comprises a micromachined array of individuallycontrollable, electrostatically movable shutter elements.
 56. Apparatusas defined in claim 50 wherein said optical assembly further includes asingle illuminating objective lens between said array of illuminatingoptical shutters and the sample, and a single collection objective lensbetween the sample and said array of collection optical shutters. 57.Apparatus as defined in claim 50 wherein said optical assembly furtherincludes an array of illuminating objective microlens elementsrespectively aligned with the optical shutters of said array ofilluminating optical shutters and positioned between said array ofilluminating optical shutters and the sample, and an array of collectionobjective microlens elements respectively aligned with the opticalshutters of said array of collection optical shutters and positionedbetween the sample and said array of collection optical shutters. 58.Apparatus as defined in claim 50 wherein said array of illuminatingoptical shutters and said array of collection optical shutters aresubdivided into noninterfering zone arrays and electromagnetic radiationis collected simultaneously from said noninterfering zone arrays. 59.Apparatus as defined in claim 50 wherein said array of illuminatingoptical shutters and said array of collection optical shutters eachcomprises a plurality of rows and columns of shutter elements. 60.Apparatus as defined in claim 50 wherein said array of illuminatingoptical shutters and said array of collection optical shutters eachcomprises an array of radially distributed shutter elements. 61.Apparatus as defined in claim 50 wherein said array of illuminatingoptical shutters and said array of collection optical shutters eachcomprises a linear array of shutter elements.
 62. Apparatus as definedin claim 50 wherein said array of illuminating optical shutters and saidarray of collection optical shutters each comprises a circumferentialarray of shutter elements.
 63. Apparatus as defined in claim 12 whereinsaid optical assembly comprises illuminating optics for sequentiallyilluminating said plurality of volume elements and collecting optics forcollecting electromagnetic radiation emanating from each of said volumeelements, said illuminating optics comprising an illuminating bundle ofoptical fibers and illuminating control means for sequentiallyactivating each of said optical fibers for directing illumination fromsaid source to the sample, said collecting optics comprising acollection bundle of optical fibers and collection control means forsequentially activating each of said optical fibers in said collectionbundle for directing collected electromagnetic radiation from the sampleto said detector.
 64. Apparatus as defined in claim 63 wherein saidilluminating control means comprises a first rotating mirror forsequentially directing illumination into the optical fibers of saidillumination bundle and wherein said collection control means comprisesa second rotating mirror for sequentially directing collectedelectromagnetic radiation from the optical fibers of said collectionbundle to said detector.
 65. Apparatus as defined in claim 63 whereinsaid illuminating control means comprises an array of individuallycontrollable illuminating optical shutters respectively aligned with theoptical fibers of said illuminating bundle and wherein said collectioncontrol means comprises an array of individually controllable collectionoptical shutters respectively aligned with the optical fibers of saidcollection bundle.
 66. Apparatus as defined in claim 12 furthercomprising a spectral analyzer disposed between said optical assemblyand said detector.
 67. Apparatus as defined in claim 12 furthercomprising a temporal interferometer disposed between said opticalassembly and said detector.
 68. Apparatus as defined in claim 12 furthercomprising a spatial interferometer disposed between said opticalassembly and said detector.
 69. Apparatus as defined in claim 12 furthercomprising a Hadamard encodement mask disposed between said opticalassembly and said detector.
 70. A method for determining acharacteristic of a sample of material by the interaction ofelectromagnetic radiation with the sample, comprising the stepsof:sequentially illuminating, with an optical assembly, a plurality ofvolume elements in the sample by directing electromagnetic radiationinto the sample with an intensity distribution in the sample that dropsoff substantially monotonically from a first region in a first opticalpath; sequentially collecting, with said optical assembly,electromagnetic radiation emanating from each of said sequentiallyilluminated volume elements with a collection distribution that dropsoff substantially monotonically from a second region in a second opticalpath, said first and second regions at least partially overlapping ineach of said volume elements, said optical assembly comprising at leastone array of field stops whose dimensions are large compared to aquotient of wavelength of said electromagnetic radiation divided by aworking numerical aperture of said optical assembly, measured from saidfield stops; and detecting the collected electromagnetic radiationemanating from each of said sequentially illuminated volume elements toproduce a response representative of said characteristic in each of saidvolume elements.
 71. A method as defined in claim 70 wherein the stepsof sequentially illuminating and sequentially collecting are performedwith said optical assembly, wherein said at least one array of fieldstops comprises a single array of individually controllable opticalshutters.
 72. A method as defined in claim 60 wherein said methodfurther includes the step of moving at least a portion of said opticalassembly with respect to the sample so as to vary the locations of saidvolume elements within the sample along the optical axis of said firstand second optical paths.
 73. A method as defined in claim 70 whereinthe step of illuminating a plurality of volume elements includessimultaneously illuminating two or more noninterfering volume elementsand wherein the step of collecting electromagnetic radiation includessimultaneously collecting electromagnetic radiation emanating from saidnoninterfering volume elements.
 74. A method as defined in claim 70wherein said array of field stops comprises an array of individuallymovable micromirrors, said method further comprising sequentially movingthe micromirrors of said array between an active position for directingillumination to the sample and for directing collected electromagneticradiation from the sample to a detector, and an inactive position.
 75. Amethod as defined in claim 70 wherein said array of field stopscomprises an array of individually movable micromirrors, each of saidmicromirrors comprising an off axis segment of a paraboloid ofrevolution, said method further comprising moving pairs of saidmicromirrors between active positions and inactive positions, onemicromirror of an active pair directing illumination to the sample andthe other micromirror of the active pair directing electromagneticradiation emanating from the sample to a detector.
 76. A method asdefined in claim 70 wherein the step of illuminating a plurality ofvolume elements includes directing illumination through a bundle ofilluminating optical fibers.
 77. A method as defined in claim 70 whereinthe step of collecting electromagnetic radiation includes directingcollected electromagnetic radiation through a bundle of collectionoptical fibers.
 78. A method as defined in claim 70 wherein the step ofilluminating a plurality of volume elements includes modulating theillumination of the sample.
 79. A method as defined in claim 70 whereinthe steps of sequentially illuminating and sequentially collecting areperformed with said optical assembly, wherein said at least one array offield stops comprises an array of individually controllable illuminatingoptical shutters and an array of individually controllable collectionoptical shutters.
 80. A method as defined in claim 70 wherein the stepsof sequentially illuminating and sequentially collecting are performedwith said optical assembly, wherein said at least one array of fieldstops comprises an array of individually controllable illuminatingelements and an array of individually controllable collection elements.81. A method as defined in claim 70 wherein the step of illuminating aplurality of volume elements includes illuminating said volume elementsat different times with sources having different spectra.
 82. A methodas defined in claim 70 wherein the step of detecting the collectedelectromagnetic radiation is performed by an array of detector elements.83. A method as defined in claim 70 wherein the steps of sequentiallyilluminating, sequentially collecting and detecting are carried out withbiological tissue as the sample.
 84. A method as defined in claim 70wherein the steps of sequentially illuminating, sequentially collectingand detecting are carried out in vitro.
 85. A method as defined in claim70 wherein the steps of sequentially illuminating, sequentiallycollecting and detecting are carried out in vivo.
 86. A method asdefined in claim 70 wherein the step of detecting includes producing aresponse representative of at least one pathology.
 87. A method asdefined in claim 70 wherein the step of detecting includes producing aresponse representative of cancer.
 88. A method as defined in claim 86further including the step of presenting the response as an image of thespatial distribution of said at least one pathology.